I have heard many times people say finasteride loses its efficacy over time. However, you have said its just the naturally balding process taking over. Does that mean then, finasteride never loses efficacy and its just the balding gene taking over?
Think about a tug of war — one side (finasteride) pulling against the other side (genetics). The genes will eventually win the tug of war in most people (using a multi-decade time scale). Remember, the balding pattern you are inheriting can be almost any pattern. The worst pattern, the Norwood Class 7, is only present in 7% of the population.
Balding is progressive, but the speed and the degree of the balding process varies. There is no doubt that finasteride works constantly against the balding process but sooner or later, the balding pattern you inherited MAY be achieved.