I'm 60 & much slower on hills than in the old days. OTOH I used to ride 250 miles/week, now much less. For a hilly tour I'd need to do more intensive training. Also the slower metabolism means stricter diet to keep body fat down. Heh, I remember one top US racer whose dad told him the best training exercise was to put the hands on the edge of the dinner table & push. A lot of tourists say to just ride into shape but I find riding quite easier when I'm on the lean side.
As to saddle comfort, age hasn't been a major problem. I haven't found the perfect saddle but have a couple that are reasonably comfortable.