I do a once a year check with x-rays, bloodwork (once old/big enough), fecal test, and general check-up. I also send in their fecals for tests every 3-6 months, as well (no chams sent with the fecals). Another good thing to keep track of is their weight, as well, along with everything
@Flick boy said, too. Granted, my vet is very close, and it was easy to get my chams in and out without much stress, so it could be different for you.