Snakes eat carrion?

[Bogertophis]

...I have been wondering if there's anything to offer as an alternate to rats, or mice. I'm sticking with rats. Since I do expect him to live another 28 years though, I do wonder if rats can be substituted occasionally...

Many snake-keepers feel it's more natural & likely more healthy* to vary the diet of captive snakes, since that's certainly what happens in the wild. (*Since not all prey animals offer the exact same nutrition, in terms of %'s & trace minerals.) The only thing I'd caution you about though is if you're talking about a ball python, keep in mind they can be VERY opinionated. While some may happily accept other prey items, not all of them will, OR, they'll get stuck on the "new thing" so be careful what you try. If the new thing is not 100% accessible for you to provide in the future (either due to availability where you are or the price is prohibitive) I'd think twice before 'opening that can of worms' (figuratively speaking ).

Years back, when I raised rats, mice & hamsters, I varied the diets of many of my snakes. Many seemed to relish the occasional changes, or at least they submitted no formal complaints. Some also tried chicks. Your budget might also be a consideration, since things like ASFs (African Soft-Furred rats) cost a lot more than the domestic rodents.