I ride for exercise and recreation, but very rarely for transportation. Sometimes it's 30 minutes to an hour in the neighborhood. I'll push myself as hard as I can and ride some hills too.
I live next to a state park which is a mecca for bike riding. I go there a couple of times per week and spend the whole afternoon riding. I'll push myself to my limits for a hour, then take a break and have a beer or two. As the afternoon progresses, my riding becomes more recreational.
I find that when the endorphins start to kick in, the pain actually becomes pleasant. Some soreness the next day makes me feel like I accomplished something. I've been lifting weights for many years too. You learn that it's worth it to endure some pain in order to get some gains. As long as you're not injuring yourself.