Everyone seems to have different philosophies, I wouldn't worry about shooting too much though, haha.

Personally I tend to shoot 20-30arrows, at a time, I should shoot more often but I don't I think if you shot 2-3x a week 20-30 arrows per session, you'd be doing great.

Also focus on quality shots.....don't just shoot to shoot, make em count! shooting too often, or past the point of becoming tired, will only reinforce bad technique....something nobody wants to do!

So if you feel yourself getting tired, shaky, etc....stop also a day to rest isn't a bad thing either, let those muscles recover, you should be able to know your own body.....just be smart about your shooting.

Also you may want to hold the bow at full draw for 30sec.....working up to 45 or 60secs......different muscle groups/fibers etc...... build up that endurance, just my point, be smart about what you're doing, know what you're doing and why you're doing it, and I think you'll be pretty awesome with a bow in no time.