I don't think timing affects purchase prices in that way. What I mean is, it does, but you won't know which direction because there are a lot of variables. Sometimes it will be cheaper earlier, sometimes later. Sometimes a hotel will have a lot of vacancy in the upcoming days and need to sell their rooms out fast so it's really cheap right before the said date. Other times they will be relatively full and prices will go up. Don't worry too much about it and just bid accordingly - you'll still get way better deals than most other sites. :)