Both F/T and live have their pros and cons. Live rodents can harm your snake, but it's rare if fed to your snake correctly. Also, f/t can be a potential danger if you feed a rodent that hasn't defrosted completely or has "cooked" if heated too warm.

F/T rodents can last over a year if vacuum packed, or a couple of months if stored in a zip-loc bag. They can be left overnight without a problem, but the ones left overnight should be disposed of. If you have a snake that won't eat a f/t rodent, you can refreeze it once. You may be able to freeze it a second time, but I wouldn't recommend it. Each time you freeze the rodent, the freezing process will break down the cells and it will become mushier. After a second time it's pretty mushy and you already risk it breaking open with all of the unpleasantness that can bring, so I can't imagine what would happen if you tried it a second time.

There are a number of F/T vs. Live discussions on this forum... just do a search for "feeding live".