I've done them, just to prove to myself that I could, but I didn't enjoy them.
I'm not fast enough to complete a century in 4-5 hours. Four to five hours is about my limit for any activity--work, sleep, traveling, visiting people, whatever. Cycling is no different for me.
Last century I did, I arrived home completely bored, antsy, and upset. Didn't want to even look at the bike for two days. Did a nice metric today with the club. Just under four hours. I arrived home a happy man, looking forward to tomorrow's ride, and Sunday's too.
So ride what you want to ride. Me? I'll stick with 50-70 milers, thanks.
FWIW, I won't be doing my favorite ride this year, the
Highlander Cycle Tour, because they've eliminated the 70-mile cut. Since this year's route goes around a lake, I can't make my own cut either. At least not without a snorkel.