From the teeny tiny bit I know about orbital mechanics, I’m gonna guess “polynomially”. T^2/R^3 = k, and all that. My non-rocket-scientist brain has dumbed this down to a verrrry eccentric orbit, so it’s not actually decaying in my mind, just doing the normal approaching-apogee slowdown?
My kids are about 5 years away from being able to make those kinds of arguments. I’m happy with their steps towards it, though. 
Keep us posted!
