[Etheryte]

Out of curiosty, why the last one? If you update a package, generally you don't need the old version, why would you keep it around? I can imagine this being useful in some edge cases, but as a global setting, I'm not so sure.

[nuxi]

I got bitten by broken upgrades in the past, when you were still able to simply "brew switch" to the old version if it was there. In addition the cleanup time is annoying when upgrading a lot of packages, so I kept the setting.