Hi, Diplome!
Pre-booking cuts costs, simples. OK, I/we are the "comfortable retired" who are flexible and can plan ahead, and our trips to our '2nd home' in
Virginia usually get booked within a couple of weeks of returning home from the previous one
For those with different scenarios, the pricing scales can be a beeeetch. Short-bookings cost a fortune.
The one thing I
will say for Virgin [about to test reliability etc.] is that
this time they were the cheapest car rental by a mile!! A 3-week SUV for £534 with Alamo [with ALL the insurances] out of IAD that undercut everything else on the Web - IIRC, the BA equivalent was over £700 when booked with the flights.