Long explaination short: It depends on the genes of the animals in question. Inbreeding brings recessive traits to light. If a snake has hidden genes that cause health problems, inbreeding will get you unhealthy snakes. If a snake lacks these genes, then inbreeding isn't much of a problem. In general, the more you inbreed, the more likely it is you'll uncover some unpleasant trait, which is why most breeders prefer to outcross their lines. Sometimes this is not an option, and thus inbreeding has its uses. It's a technique that's best used in moderation.
-Kat