But going ask anyways... whats the longest you should go inbetween changing substrate. I mean that as in cleaning the tank changing. I haven't changed my ball python and red tail boas in around 2.5-3 months. When they defecate and urinate, I scoop out a big chunk of it. Then replace what I take out. But, when would be a good time to change the entire thing? Theyre not getting any skin infections, or anything like that. Just asking to be asking. Read that every 6 months is good. But, wana know for sure...