Fairly fast...the hatchlings themselves can be about 18-20", with a sturdy build. They do eat often too. Your room temp. would be fine, just need a UTH under a portion (about 1/8th) of the cage floor. When I kept & raised bull/gopher snakes, I lived in the desert & my house ranged from 70-83* (w/ HVAC that kicked on below or above that.) These are great hissers, btw...mostly bluff that they outgrow, but it's fun while it lasts. They're not pansies...![]()