General administration is similar to Arch or any other regular distro. Package updates necessarily take longer because of recompiling but that's just CPU time. There are precompiled versions of big popular binaries (open office, Firefox, etc) that allow you to save a lot of time if you want.

Where you lose time is in trying to optimize your system and packages using the multiple switches that Gentoo provides. If you're the OCD twiddler type, Gentoo can be both extremely satisfying and major time sink.

I don't understand the time sink. Isn't spending time knowing intricate details about your system a good thing? You know better than most if you've gone that deep.