Caveat: I have not read through this whole thread so some of what I say here might have been mentioned
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It depends on the nature of the animal we are working with. We already have some very clear cases of inbreeding depression in the hobby where the family trees look like a palm tree. A great example would be Granite in carpet pythons.
The flip side is that we have some unique cases where the species we keep have gone through an evolutionary bottleneck prior to entering the hobby and there seem to be minimal issues with inbreeding. rough-scale pythons and crested geckos would fall in to this category.
As it pertains to ball pythons, given the extensive geographic range they have there is no reason to suspect they have bottle-necked so it is fairly safe to assume there will be eventual inbreeding depression over time. What, exactly, that would look like is going to depend on the specific “genetic burden” that your founder animals have. Anecdotally, I would say that one or two generations of inbreeding (parent to child or sibling to sibling) should, by and large, not have a significant detrimental impact but I personally would not go much beyond that.