It strongly depends on the person, some are faster than others.

JCTI takes at least an hour for nearly all people with high scores. 2-3 hours isn't too much.

CFNSE takes 2 to 5 hours, according to the estimation on the website - it's an accurate estimation IMO. A possible strategy is to do it "quickly" (for 2-5 hours or so) and leave everything you couldn't answer definitely for the last. Then spend 30-60 minutes on each of those. I think this isn't going to artificially inflate your score, and I'm quite certain that someone with 100-110 IQ can't figure out the patterns for any of the hardest questions, even if he spends hours/days on each.