On average, when does hairloss seem to accelerate the fastest?

[JSmyth]

I am currently 26 and have mild frontal thinning with slightly receded corners. I have been on finasteride for 4 years (currently taking 0.5mg every other day).

I am curious when, on average, an individuals pattern of hair loss becomes evident. I want to get a HT at some point but I am not jumping into anything without having a good idea of where my hair loss is headed.