If you get 3 or 4 years (which seems you will) you'll keep going. When I started finasteride I said the same thing..."once I get older I won't care and I can stop taking it" that was 20 years ago. It's very tough to accept that you're ready to go bald, in 4 years your not going to decide it's OK to be bald. I have an incredibly hot wife, kids and a all around good life but I'm still taking it. I haven't decided that I want to be bald.
finasteride might not work for everyone but I think the one gaurentee is if it did save your hair and you stop taking it - you will lose all the hair finasteride saved.