I live in southern Colorado. That gives me a pretty good mix of flat desert, alpine climbing, and rolling foothills. If my average speed gets too much above 10-12, I need to find a mountain to go over.
I've only managed one gravel ride this year and it still had a 10 mile descent. I love those huge climbs and seem to be a pretty solid descender. It's funny because everyone and their grandma passes me downhill on a road bike.
I'll be doing a 115 mile ride this summer that's as flat as it is windy (ugh). I think it's what most people love about these bikes. It sounds like a lot of work. I'm doing it because of proximity and schedule mostly.