I pride myself on being to get up any hill. I don't care how slow I go. I did a 10 mile climb in Spain, at about 3-5 mph.
Only 2 hills have defeated me in the 15 years I have been cycling. Both were in the Berkshires, involving roads I had no idea of, in terms of how long and how steep. When I think of it, one was a ride recommended by our innkeeper and the other was one one a friend got from Ride With GPS, but he didn't really pay attention to the grades. Both had long, long climbs with 15-20% grades for parts. The first one, my DH dropped me and when I saw my friend walking, mentally I was done. We got to the top, got on our bikes, to find there was another long and steep climb, with another summit. I did that part. For me it's a lot psychological. If DH stays with me and talks me through it, I do a lot better. At times, I can do the self talk (I did this on another road in the Berkshires that was just painful). I am not sure how I would do in the west, where climbs are long and not quite as steep. Most of what I do are short and steep.