I've always tried to take the stairs as I am quite fit, am mindful of others need, and in an attempt to burn off cake. But on one cruise I was many floors away from the action and determined that the stairs wouldn't beat me, I continued up and down all week. It took weeks after getting home for my tendons to recover. Now, I try to pace myself a bit better.
Stairs are hard work for a lot of able bodied people but I agree that wheelchairs etc should get priority, that's just manners.