i have been on propecia for 3+ years and it has not maintained my hairline. It still receding and thinned out more. It might have slowed it down though, I am not sure.
I was on Propecia and it did absolutely nothing for me. My hair was falling out the most it's ever fallen out while on Propecia. I also had a lot of sexual problems. Some people do good on it, some don't. I didn't.