RChung

It depends on your goals. Are you thinking about competing, or are you just trying to stay up with your friends, or do you have a goal to ride across the country once you retire, or do you just want to know for your own curiosity?

Nonetheless, here's my advice for anyone who is trying out some new technology (whether heart rate monitor, or power meter, or even a speedometer if you haven't been using one): just ride as you normally do for a few weeks, but start keeping a little notebook about your ride. In your notebook, write down how far you went, how hot or cold it was, how windy, how well you ate or slept before the ride, and, critically, how you felt both during and after the ride. Lots of people use a rating scale of "perceived exertion" on a 1-10 or 1-20 scale.

Importantly, just record those things but don't change anything yet. That's both because you're trying to set a baseline for comparison, and also because you don't yet know enough about your baseline to go changing it.

Best of luck. Enjoy your riding.