My wife has done 60 on a comfort. I've done 100. I looked at the specs. Tuires are 700X40. I'd put 700X 35's just to have a higher pressure tire. You'll have a bit lower rsistance if the tires are higher pressure than the 40's (not sure of rating on stock tires, but most aren't very good tires). Upgrade tires.
I've seen riders doing centuries on comfort bikes,mtn bikes, every kind of bike out there. I've seen one legged women do centuries with one leg( no prost?).
Biggest obstacle for most riders is themselves, not the bike.
