Im not really that interested to know which rodents are best. If anything you wouldnt have to do it with snakes it would just be using the rodents and analyzing their nutrient levels. Which also all depends on their diet. That would be something that could be done probably pretty easily.
Maybe the ones that lived longer just had better genetics. You cant really prove anything with that. Theyre all the same animal but genetics are a huge part of it.
I know the temp and humidity does matter TO an extent. But some people feel it has to be EXACT. Sure drastic changes are bad but a few variations isnt bad...