Vet check isn't a bad idea. I generally get my snakes from reputable breeders, but I still keep them apart from my established collection until I've determined that they don't have something obviously wrong with them. I'm looking for mites, RI's, infection, scale rot, mouth rot. Those sorts of things. If they eat weekly, shed and poop like they should over the period of 2 months or so, I take them out of QT.

The idea is to keep them away from your established snakes so you don't spread any unknown diseases between the two. Sticking to getting snakes from reputable sources will greatly reduce, but not eliminate the risk. That is why QT is necessary. You never know what the snake could pick up at a show either.

Some people have stricter QT proceeders including a completely separate facility for their QT animals. I can not afford such luxury at this time
There is a sticky somewhere here that talks all about the QT procedures.