They grow very slow... the bulk of their growth is within the first 15- 20 years, then its slows down even more. My two year old still fits in my hand quite nicely
I've had him since about 3 months of age, but never bothered to really keep any growth records. There aren't a whole lot of great caresheets on redfoots out there, tortoisetrust.org is your best bet for accurate info. Best to find other keepers and go from there, that's what I found worked best.
They are really great tortoises... they actually recognize their keepers as their caregivers and are not shy at all. Mine will greet me every time I talk to him, open his cage, or walk in the room
If you have any questions, just ask