If you dont pace yourself you will burnout quickly. I like the mountain bike because of the durability and it is great for cutting across vacant lots.and it hold up better to carrying stuff.

Hey that's great, congrats on your first run. Boy I thought mine was a haul at 12 miles, 1 hour each way. Boy you are ambitious, but good work.
I listen to audio books on my ride. I know what is said about listening to devices while riding, but if I didn't I would get bored out of my skull on a 1 hour ride and quit.

4 hours a day, 5 days a week, on a mountain bike? That's impressive.