I prefer to keep mine separate, but I always use specific terminals / screen sessions for (mostly) the same type of work (admin, specific projects, web dev, etc

I prefer to keep mine separate, but I always use specific terminals / screen sessions for (mostly) the same type of work (admin, specific projects, web dev, etc.) so each have their own history, as well as keeping a per-directory record. So far over 130000 command lines (with timestamp & cwd) for past 2.5 years, just on my laptop.