Hard to say because i have two copies. I think close to 50 hours on my new town but my old town was 100+. My second copy wasn't played as much (actually thinking of returning it)
I played well over 1050 hours with both of my American and Japanese 3DSes combined, although I've spent more time with the latter. I'm planning to stop playing Animal Crossing: New Leaf this year because I've pretty much seen everything they had to offer.