In general, it is harder to reverse even a small recession than to thicken up a larger thinning area like the crown. The frontotemporal hairline is more sensitive to DHT than the rest of the top of the head. Most people's temples don't thin before they recede, they just recede(unlike the crown which always thins before balding completely). That is, they go almost directly from full temples (NW1) to slick bald temples (NW2). The miniaturisation in this case is so dramatic and rapid (as opposed to the slower miniaturisation that occurs on the crown, and even slower on the top) that it takes only one or two cycles for the hair to shrink to near-invisible vellus without any cosmetic value. That said, it should be possible to recover atleast some of the area with prolonged treatment, but it is VERY rare to recover all of the area with ALL of the original hair and original average diameter (adolescent density). But then again, adolescent density is not really necessary from a cosmetic point of view. 55-70% of the adolescent density should suffice.
Cheers.
Arkim