I'm a few posts behind the curve on this one, but my Denali coasts for a very long time as well. I don't think the tires really make a difference as I'm on 25mm tires. I think a lot of it could just be the inertia of the bike itself haha.

I'm running a WTB Speed V saddle on mine as I prefer mountain bike saddles. It's very comfortable and about $30 on Nashbar or Amazon.