If you bid on 4* and there are no 4* properties available for those dates in that neighborhood, then your offer will be refused. HOWEVER, if there are Resort* or 5* properties available, and if they are willing to accept your price, then you may be upgraded to one of those. This is not uncommon. You should also look at the list rates for potential Resort* properties, so that you don't overbid.
Another thing to keep in mind is that if you are happy with the hotel and price you already won, it is sometimes possible to extend that stay for a number of days either before or
after, up to as many days as you have already booked. This is done from your confirmation page when you are logged in to Priceline, and viewing your original booking. There is a button for "extend your stay". This function will guarantee the same hotel and the same price, but only if the hotel has vacancy for the period you want to extend into.
Also, be aware that the list rate may be LOWER for the days you want to add, and so you might get the best deal by starting an entirely new offer on Priceline, although you risk winning a different hotel.
Please always remember to start your bidding through Our Priceline Link
either in a moderator's signature line, or from one of the Priceline links here in the pages of BFT, and never from an email you receive from Priceline. Thank you!