My max HR is 185. I typically ride 20-25 miles between 14-15 mph (avg. speed) with my HR somewhere around 145-155 which is 78-83% of max. I don't feel overly tired - it's a comfortable pace for me. I usually ride 3 days a week all within these numbers.

Now my questions:
1. Is this a good zone to be in?
2. Would I benefit in any way by forcing myself to stay at a lower HR? If so, what % HR?
3. Or, should I be shooting for a higher HR?

I've read about training zones, etc. but they are a bit confusing. I don't see why you would intentionally keep your HR lower than what you are capable of sustaining. I can understand the benefits of pushing oneself. Can anyone clear this up for me?