Booking last minute is not always best. I tried to book a hotel for late April. Someone else had gotten the Sheraton Safari for my dates for $41/night. They won their bid on Priceline in January. I guess the Sheraton (and other hotels in the LBV zone) had little availability by the time I started bidding one month out since all of my bids up to $55 were rejected. I ended up winning a room in the Universal zone a few days before I left.
Since Priceline is used to dump unsold inventory, if availability decreases, rates may go up as the hotel fills. The same could apply with prices on the hotel's website. The bidding-for-travel site shows multiple cases in which low bids that were accepted at a particular hotel were rejected for other people that won the same hotel at a higher rate. Not only does availability change, but winning bids for each hotel do also.
My tip would be study up and find out the lowest rate accepted. Don't exceed that amount when bidding early. Keep bidding periodically without raising your price. You never know when a hotel will release rooms to Priceline at that price. A back-up reservation is a good idea just in case.