I think inbreeding rodents for more than 2 generations can have some adverse effects. I am not sure how well your mice grow and breed but obtaining good stock is important. I have seen slow growing and producing mice that tend to get sick a couple of times at pet shops.

Your best bet is to get breeders from a large rodent breeding facility because they tend to have good genetic diversity. Even better drop the mice and switch to african soft furs. On the other hand, if your mice breed and grow well I wouldn't worry about inbreeding for a couple of generations.

This is why you should get a very large rodent colony with a diverse gene pool. Look at this as a great opportunity to expand your rodent colony and with it your snake collection.