Up until recently about 12 hours a week. Flatwoods is nearest to me, so I ride there alot, Santos is alway my first choice but it is too far to ride regularly, Alafia and I have some history now, and it is great!
Welcome to the world of mountain biking, it is awesome, and there are a bunch of bike addicted freaks (including myself) on this forum who will be happy to share there experiences.
Here is my unsolicited advice:
Make sure you have a comfortable helmet.
Get a good hydration system. i.e. Camel back etc.
Padded pants (you have no idea how important that is!).
Keep a spare tube and a compact tool kit.
Buy band aids. (not kidding!).
Aleve, keep some on hand at all times.
Keep your bike clean(ish) and in good working order.
Keep your arms and legs in the vehicle at all time (especially your legs,it is a long story).
Ride Ride Ride. It will change your life.