My Wife and I just signed up for a 100K in April (Tierra Bella, Gilroy, CA). We shouldn't have a problem with the distance since we've already done a casual 55 miles from our home to San Jose, but given my Wife's aversion to hills I was a bit concerned about the 2350 feet of climbing required for the 100K. I was really surprised when DW suggested we ride up Lone Tree Road which dead ends up in the hills. We stopped at a gain of about 600', only a baby step given the top is at 3200 feet and our home at 300 feet, but I'm confident now I can nudge her to try some of the back road rides around here. Definitely a good day.
I'm going to ride this thing once or twice a week until I can get to the top. 10 years ago I was still running and might have made it up 6-7 miles, but I'm guessing from our house it may be as much as 12-15 miles to the top. I'll find out in a few months.