My female outgrew her 110 qt sterilite (3 foot long with some height) when she was around 3 years old.
I wouldn't put a male in a cb70 for life either though. That's too small for any adult dum. Particularly since they're burrowing snakes and like thick substrates and leaf litter.
Technically, dumeril's grow for life. Just the rate of growth slows down by a lot when they're around 5 years old.