Does Rover have a different pay policy for long term reservations?

As an independent contractor, you decide how you want extended stays to be processed and Rover will do it. DV doesn't automatically break up or reformat any stays. The sitter dictates that.

If you booked it as one very long stay, then, yes, the payment would be at the end on both Rover and DV. However, you could choose to have the client book it as a series of one week or two week stays, so that you do get paid earlier. However, I would bet that some customers may not agree but you could always suggest it.