I'm probably going to repeat some previous good points, but here goes.....
I vote longer (and the 90 min special is a big marketing plus IMHO). I am one of the older dogs, so quite frankly it takes me a little longer. Having a longer session works better for me. Also, since about 99% of sex is between the ears, a longer session usually (for me anyway) ends up being a more intense and enjoyable time because there isn't a lot of time pressure.....for either person.
Generally speaking, the idea that a lady may see other guys in a day doesn't bother me...I prefer not to think about it (remember the 99% in the head comment?). Having said that, I fully appreciate Andy's comments about a) wanting to feel fresh; and b) the comment about being a little older......though I am somewhat older still.
This was a good question, and brought out a lot of good posts. Thanks for starting the thread Whitney, and I hope that the responses helped you out.