My first game took me roughly 63 hours to finish. I did however spend about the last 20 hours of it leveling up in the Northern Cave, getting KotR and Omnislash, etc. I thought I had to level up that much to have any kind of chance at all against Safer Sephiroth. If I'd known that a single Omnislash would kill him quicker than it takes to get to the good part of One Winged Angel I could've finished it by hour 40!

In my current game I'm at hour 40 and right at the begining of disc 3. But I'm trying to get absolutely everything in the game (except Aeris' and Cait Sith's limit breaks, because Aeris dies before she can be useful and I hate Cait Sith that traitorous sonuvabitch), so I expect I might go up to 60 hours, or more.

I'm also going to beat Sephiroth sans KotR or Omnislash. They make it way too damn easy. Plus, you don't get to hear the good part of One Winged Angel