I remember Gentoo taking more than a full day to compile on my computer back then. It did teach me a lot though, will always have a soft spot for it.
I installed gentoo on a workmachine at a new job, like a dual xeon something with 64gb ram back in a time where 8gb ram on a worstation was plenty. I had a blast. It took "only" like 3 hours to get my usual to go system.
Unfortunately I need haskell on my workstation (xmonad) and ghc can easily take alone like 5-20+ hours compile time on older computers. I compiled ghc a few times on an old t41 - it took more than a day.
Still, gentoo is my first choice. I run it on a few root servers and every workstation.