It would likely be easy enough to take a day off each of the two hotels in Hoi An--making it 3 nights at each instead of 4. Then we could add one more night in Hanoi and one more at Halong Bay. Apparently the boats get further away from the crowds if you're out for 2 nights. Was that your experience, Ladouca?
I had been researching the hotels on TA, CFW; I intend to ask the tour agent whether he can offer one of the Hanoi Elegance hotels instead.

We spent 12 days in northern Vietnam - just Hanoi, Sapa and Halong Bay. One night on Halong Bay is plenty - we never felt like it was crowded, although there were other boats around. Two nights and it will be more of the same - look at some of the itineraries of the boat companies - the two night trips are not separate itineraries from the one night trips.

The Hanoi Elegance hotels have a great reputation.

it looks fantastic to me... i might subtract one hoi an day and add to hanoi... it is such a wonderful place to visit....

we had to skip hue because all flts were cancelled...

you are missing nothing by skipping HCMC... some like the delta, some not... i chose to skip it...

hoi an is simply the best... ask for a river facing room at vinh hung.... pool is lovely but it rained the whole time we were there...

yaly is fantastic for clothing...

The comments to date have been really helpful, and have assisted in shaping some of my decisions. We did opt for spending 3 days in each of the two Hoi An hotels, instead of 4 days each. With that extra time from Hoi An we have changed to 3 days and 2 nights at Halong Bay (instead of 2 days, 1 night), and an extra day in Hanoi. The tour company readily switched us to the higher rated Hue Orchid (instead of the Romance Hotel). I have been trying to contact the Hanoi Elegance Hotels, and so has the agent, but no response yet after 4+ days. Meanwhile the new Imperial Hanoi Hotel, which gets excellent reviews, has been offered as an alternative to the Hanoi Boutique.
I'd have to say that to date the tour company is putting all this in place in a very accommodating way, and as far as I can see cheaper than we could arrange on a DIY basis. We're getting private car and driver, airport transfers, 2 business class flights on Vietnam air, some tours, and accommodation w breakfasts and some lunches for just over $1000 each, 2 persons for the 17 days/16 nights.

Although it may not seem like it from the posts above, most of the folks on this forum (including rhk above) recommend just one night on Halong Bay. I followed that advice and was not disappointed.

We stayed 2 nights on Halong Bay. IMO, if you are not going to kayak or do anything active, you should not stay the second day. We were the only passengers in our group that stayed for a second night.

I agree with the other posters...I would definitely skip HCM and the delta in favor of the northern locations. I still feel you have way too much time in Hoi An. Hoi An can be seen in one day, although it is delightful to walk around a second day as well. Unless you are having clothing made and love to shop, I really don't see a reason to spend a week there. You can wander around the town for part of a day and then spend the rest relaxing poolside or at the beach. I do not think I would bother with splitting time between different hotels. It is easy enough to take a taxi to the beach or into town, depending on where you chose to stay. How many days do you want to lie on a beach? Perhaps I am jaded as I live in Florida and have sunshine all year round.

IMO, I would opt for more time to Hanoi and if possible, time in Sapa depending on the weather at the time.

Interesting comments; thank you very much. Wow--we've gone from, initially, 8 days in Hoi An to no more than one or two days!
In general, we prefer to have at least 3 nights in one hotel, and not to be going elsewhere every second day. It comes down to individual travel style, doesn't it?
Because we might be extending our Vietnam trip yet again to more than 3 weeks from the present 17 days, I should start a new thread about other possibilities.

Will - If you click on my name, you can read my trip report of our 3 1/2 weeks in Vietnam. I agree that a 3 night stay is best... I only meant to say that you can easily see Hoi An in 1 day. It is magical though and you will enjoy spending several days there.

I have (re)read your trip report, Dgunbug. It is very evocative and full of great detail. Of course now that I have a better idea of the places you refer to, it means more than when it first appeared. I notice that in June you were glad you'd done the second night on Halong Bay. Now I understand what other posters meant by the second day being "more of the same."
As for Halong Bay, we're looking at one of the smaller junks, 4 cabins, that gets into the more remote places. It leaves from Cat Ba island, which you get to after 2 hours by road and 45 mins by hydrofoil. It's an eco-tour boat that apparently has permission to go places the bigger ones can't. But who knows what we'll decide when the time comes?
It looks now as if we will be spending about the same time as you did, 3-1/2 weeks, so your trip will be an important template. Many thanks.

Will, if you're spending more time, I can't recommend a trip to Sapa enough. It was my favorite place in Vietnam. I did a similar itinerary to Dgunbug, in a different order, without Halong Bay. Here's what I did, with a little over 2 weeks:

Saigon: 3 nights, with the first being my arrival at 11 p.m.
Hue: 2 nights, with an arrival at 8 a.m., so 2 full days
Hoi An: 3 nights
Hanoi: 3 nights, but 4th day I spent there as well, and took overnight train to Sapa that night
Sapa: 2 nights, but again, had entire 3rd day and took overnight train to Hanoi that night.
Then, Hanoi for the day, flight back to Saigon for early departure back to US the next morning.

If I could have, I would have added time to Sapa and Hoi An,for sure, and maybe Hanoi.

Yes, I agree--adding Sapa is now in our plans. I'm wondering, Jen, if you now wish you had skipped Saigon altogether for the sake of more time in Hanoi, Sapa, Hoi An, etc. I'm thinking of not going to Saigon because, like you, it would mean returning to our arrival point for departure. We can come and go from either Hanoi or Saigon, but I'm not keen on flying between them to leave the country.

Hmm. Good question. I would say no. I liked Saigon, and am glad I went. Lots of good historical sites, and I loved walking around Cholon, the Chinatown of Saigon. Totally different feel from Hanoi... more big city-like, more of a buzz, if that makes sense. I found the people friendlier there too, though that's true of most of south Vietnam. Not that people weren't friendly in Hanoi, they definitely were, but they're a bit more reserved and maybe, businesslike? Not sure if that's the word I want but you get the idea.

I will say that I would not structure my last couple of days the way I did though... I felt like I was travelling for three days straight-- overnight train from Sapa, arrive in Hanoi at 4:00 am, wander aimlessly waiting for the hotel to open so I can dump my bag, then I had most of the day in Hanoi, but no hotel... I really wanted a shower, I was tired, and in the end felt like I spent the day waiting to leave. It probably didn't help that it was kind of rainy that day. Then on a plane late afternoon to Saigon, hotel by the airport, up at 3 am to catch the big flight home. It was kind of draining. If I had a do-over, I would have planned a night in Hanoi before going back to Saigon. I would have enjoyed my last day in Hanoi much more that way.