Hi everyone,
I'm trying to fill in 9 days in Colorado with the 4 National Parks we want to visit.
Day 0 : We arrive in Denver and plan to stay there for the night.
Day 1 : RMNP. Camp there... We have a confirmed 3 day site.
Day 2 : RMNP. Camp overnight.
Day 3 : RMNP. Camp overnight (optional... see question below)
Day 4 : Leave for Black Canyon EARLY in the AM (6.5 hours from Moraine Campground). Day trip at the National Park. Stay in a hotel in Montrose overnight.
Day 5 : Leave for Mesa Verde LATE in the morning. (3 hours from Montrose). Camp/Lodge in Mesa Verde for the night
Day 6 : Leave for Great Sand Dunes LATE in the morning (4 hours from Mesa Verde). Camp at Great Sand Dunes.
Day 7 : Great Sand Dunes NP. Camp overnight. Do a night hike?
Day 8 : Drive back to Denver. Spend a day in Denver (I'm not a city tourist so a day is more than enough
Day 9. Fly back to home and work so I can plan the next trip!

Questions:
1. Is half a day enough in Black Canyon?
2. Is one night enough for Mesa Verde? Should I spend 2 nights there and one night at Sand Dunes instead?
3. Are 3 nights sufficient in RMNP? We are active hikers and I'm an amateur photographer. Would you suggest I forfeit Day 3 at RMNP and use it more productively somewhere else?

This trip is the 2nd week of September!
Thank You!

What time of year?

Personally, I love Mesa Verde and would spend 2 nights. If you can't get a room at Far View, stay in Cortez - there are several chain motels there.

Definitely 2 nights at MV and 1 night at Sand Dunes. From Sand Dunes on your way back to Denver you could check out Garden of the Gods in Colorado Springs.

You can't see anything in Mesa Verde with your time schedule. It is a LONG drive in to that park. Stay at Far View Lodge IN the park if you can get a reservation.
Sand Dunes can be a drive by, IMO

I agree with the others, cut one day from SD and tack it on to MV. Your driving times to/from MV may not include the 45 minute drive from the entrance to the actual park. That is the reason you really need to stay in the park as lodging outside eats up lots of valuable time.

You of course could spend lots more time in all of the parks but you will be able to get a feel for them, and hopefully have the option to return for longer visits to your favorites some day. Mid September should be perfect weather and smaller crowds. Enjoy!