Having done several TA, for myself and wife, it's the perfect cruise.
We've done cruises with multiple port days and we find them exhausting, up and off the ship, sight seeing, back, change for dinner.... wash, rinse and repeat, feel like you're always on the go. Yes you don't have to get off the ship, but if you've made the effort to go, why not see the sights of the port.
The long sea days give you the opportunity to enjoy the ship, catch all the things going on board and do all the activities, oh and of course eat and drink until you burst.
Going for Europe to either the Caribbean or the US in the autumn months usually means the weather get warm if you're taking the southern route, and the seas can be a bit calmer. We've done the northern route once, and it was bit more lumpy, but still enjoyable.
One thing that you will notice, as you cross the Atlantic the clocks go back, therefore you get multiple 25 hour days, good excuse to have an extra hour in your bed or visit the buffet/restaurant twice for breakfast.