dmd,
Like Gregswife, I have mostly sailed on Carnival. I have noticed that there is an option for passengers who carry the own luggage to disembark very early. Those passengers have to be ready by 7:30 AM. But, that's Carnival. You should check with your cruiseline for their disembarkation policy.
Another consideration would be the port. If you have a lot of luggage some of the ports require the use of ramps, stairs or escalators. If you have a lot of luggage, it may not be convenient. If you pack light, then it should not be a problem.
If you have an early flight usually the cruiseline is aware of it and will give you the appropriate tags for you flight. If you have a late flight, you usually can expect a little wait.
I have been on some cruises where disembarkation was go to the gangway as soon as you were ready.
Good luck.