I think the issue of replacement is something even a hobbyist like me should be thinking about. When one writes their guarantee, you should plan ahead to fully honor it with a quick and professional response, or why bother to even write it. That may mean holding the customer's payment in reserve until that health/shipping guarantee is met fully and your customer is happy. Should something occur down the road, not covered under your guarantee but still leaving you feeling your snake has not met a customer's reasonable expectation, then for me, you take the hit and you make it right. If you aren't prepared to do that, then perhaps selling snakes isn't such a good idea in the first place.
I'll never be a "name" in this business but my name means a lot to me.