i ride about 3 times a week. roughly 2 hours each ride. is there such thing as heart failure if i keep it up like this? to be exact, when i ride im usually in the 171-178 range, and i typically back off just to get down to 171.

background: 26 years old recreational rider.
goal: just to be able to pace @ 20mph over 30 flat miles under 150bpm preferably.


thanks
jacob