I have been using Gentoo for close to 13 years now. What really helps with the long compile times (I don’t have the fastest computers; my current one is a Ryzen-APU-based one from 2019) is to run emerges with low priority in the background. Out of sight, out of mind.
You can do that by setting
PORTAGE_SCHEDULING_POLICY="idle"
in /etc/portage/make.conf. This tells portage to run the emerge processes with an extremely low priority, and updates more or less trickle down in the background without disrupting system performance noticeably. You can also set other portage scheduling policies.
— Source
Cool, nice to know!