Pay varies across the board.
Regardless, half-day or full-day shoots are more practical. Unless you're paying $300 per hour or more, the overhead for a one hour shoot is not fair to the model.
I often hire models by the week and we work round the clock - it's a cool experience. Once we're into the routine (some models bring their own music selections and we work nights instead of days), productivity is maxed!
But be prepared -- if you're going to do a full-day shoot or more, don't punish your content users by stretching what should be a single set into 1,000 similar images.
-Dino