It took about 23 hours to get it booted under its own power using a binary kernel. And on the 4th day (today) I've managed to get a custom kernel working. Gentoo has been very fun to use and to customize, and it's very fast and responsive, even on my old hardware and with a hard disk, browsing heavy webpages with Librewolf is no problem at all. I've been sleeping on Gentoo for WAY to long.
My first Gentoo install was also because it was an ageing laptop that was too slow for anything else. Luckily it wasn't my only machine, since the install times for some things were quite long.