"Hills don't get easier, you just get faster". Forget who said that, I think it was Lemond. My work commute is pretty flat, so a couple of times a week I ride fast. Riding from home is pretty hilly (a commuter train separates home side from work side rides). My week end rides give me a lot of terrain options, depending on the route I take, except that totally flat is not an option.

I ride. If I want to train, I kick up the HR, and try not to over think it.