Think of your keg as a big bottle. So long as it stays sealed, you can condition a LONG time! Mine usually stay at room temperature or in my fermenting freezer a few weeks, and then go in the fridge for several more weeks. Nothing is set in stone, and often they sit out longer simply because there isn't room available in the brewfridge or freezer. It all comes out good in the end.
While you don't need to carbonate right away or keep your kegs on gas while conditioning, you do want to give them a good high pressure shot of gas to seat and seal the lid. Then place them in a reasonably temperature stable place and start brewing your next batch!
