Could finasteride be helpful many years after hair loss started?

Without having examined you or having seen any pictures, you may find that finasteride is more helpful than you think. As you know, finasteride cannot regrow follicles that are completely dead or absent, but it can reverse the thinning in existing follicles, even if those hairs are so thin that you can barely see them. Finasteride is more likely to reverse thinning in the follicles that have most recently become thin, so if some of your hair loss was experienced in the last 5 years or so, you may regain some of that density. Although you describe yourself as a NW6, you may have enough miniaturized hair that finasteride can make a visible difference. Furthermore, it may prevent you from progressing to a NW7. If you tolerate finasteride well, it is an inexpensive medication that may make a difference for you. Keep in mind you should try it for at least a year before determining if it works for you.

Finasteride probably won’t help all that much in the situation described but yes, it could potentially help somewhat to slow down the loss of remaining hair in the androgen dependent zones. It is certainly not a guarantee but yes, it could have some very minor benefit. It is unlikely to help the transplanted hairs, only some small proportion of remaining hairs. You and your doctors will want to review your story and determine if the risks and benefits are worth it. I would also make sure you take time to carefully review if there are any specific reasons why the transplants were associated with more limited grafts survival. If there are other skin or autoimmune issues in the scalp, addressing those too could help slow and prevent further loss.