It really depends on the vacation. When we are visiting family then we stick to bed time as much as possible, it's 8:30 and sometimes we will push until 9. But its more laid back, day trips places, when we do that so I want things to be more normal.
Disney is a whole other story! The first trip DS was 3 and for the most part we had a normal bed time, but it was also in the 30's most days and I was not about to be out too late in the cold. Plus, the parks closed early. This past trip at 5, we didn't get back to the room before 12 most nights. We are not rope drop people, so we would rather sleep in and head out around lunchtime. DS was fine until the last few days, the last day we were in bed at bedtime. Basically, we don't enforce it but if he is tired we come back and let him sleep.
My DS also has no problem going back to his normal schedule, I am sure it would be different if he was the type to be thrown off. Actually, when we came back we ended up having to be away for 2 more weeks cause of the hurricane and THAT threw him off more than Disney.
DH normally goes to bed between 2-3am every day, so for him he normally went to bed earlier out of sheer exhaustion.
I don't sleep at Disney, so I don't count!