Hairloss has so many possibilities. You can start balding in your twenties but at 45-50 still have a very decent amount of hair left. You could have a perfect head of hair at 40 and by the time your 45 you've lost your entire crown and/or hairline. You could lose some hair early and at 70 have pretty decent hair, you could go to your 60s with perfect and and bald by 65. There are simply too many scenarios that can fold with hairloss.
Balding or having some recession early isnt necessarily a death sentence. Just as your not safe even in your 40s even if you have good hair at that age.
However, theres a difference between balding and balding. For some people the balding /recession process is so slow and very non-aggressive, that even if they start receding early, the process will take forever so they still manage to keep a very good head of hair in later years. For some people the recession can be very aggressive, and in those cases i think its really rare for the recession/balding to stop.