I plan on spending 7 days in Milan in late September. I m thinking of staying in Hotel Garda and near the Central train station and taking day train trips to the lakes, Genoa, and maybe a couple days to vist Cinque Terra. Does this make sense? It looks like it may be only an hour by train to may locations. I would return at night to Milan (other than Cinqua Terra trip). Any thoughts?

I would only stay in Milano for a few days. Don't get me wrong I love Milano, but it sounds like you don't need to stay there. Take a 45 minute train ride up to Como or a little longer to Stresa and base yourself there while doing the lake district. Bellagio or Tremezzo on lago di Como are perfect, and on Lago di Maggiore, the town of Baveno or Stresa.

Nothing to see in Genoa really...skip it

Lago di Garda & Verona are good to, but if going over that way you should spend a night or two.

I wouldn't do Cinque Terre as a daytrip to time consuming! If your going to do it give at least 2 nights to the region.

What do you see as the advantage of using Milan as a base? Why not go immediately to one of the lakes for 2-3 days and then on to the CT for 2-3 days, then back to Milan for a day before flying out. Seven days is too short a visit to spend hours on the train every day.

I picked Milan as a base as it is close to Malpensa. It seemed to be in the middle of the Nothrern area. After flying 8 hours I did not want to lengten my travel day any more than I had to. Sounds like you think spending a couple days in each Milan, Lakes and Cinqua Terra would make more sense.
Would you fly into Malpensa, stay in where first Milan, Lakes or CT? Any particular order make more sense? There will be four ouf us should I bag the trains and just rent a car?
Thanks for your help.

You can take public trans from Malpensa to mid-Lake Como. The first hour would be bus or train, then a fast ferry ride to the Menaggio/Bellagio/Varenna area. Yes, it adds more travel time to your day, but the payoff is spending your first night in a much more beautiful spot than Milan.

You won't need a car for your stay at Lake Como, and a car doesn't add anything to a visit to the CT. The train journey between the two, however, requires multiple connections and probably 4-6 hours depending on the routing and train selection. Easier/faster to travel to a car rental agency (Como? Menaggio?), spend time doing the paperwork, finding your way to the CT, locating the second car rental agency and turning the car in? That's your call. For such a short trip, I'd keep it simple and stick to public trans.