I dont know much about guard hair, slippage (I know what it is, just not the full extent of it), prime, early, or late...is there a website, or thread, that goes into full detail about the different "stages" of fur, and when one should/should not bother putting them up?

Good Evening John,
The easiest way to learn that is to go ask a local fur buyer for some tips or pointers most will be more than happy to help you out.
I'd also suggest joining your state trappers association also I'm certain that they hold trappers education classes.

Allan

Trap when fur is prime-(there should be fur priming charts on line somewhere).Unless there is some obvious damage like scavenging etc,you should be able to put them all up.
Then you can show your put up fur to an experienced trapper or buyer and he can point things out to you so you can make a good judgement call,as you gain experience.
Some pelts even with obvious damage have good value depending on species,and market requirements.
Slippage generally means a pelt is rotting.The fur will come out in big chunks leaving bare leather.Those pelts are worthless,unless it is a small belly taint which can be cut out and sewn.

Thanks Boco!