On some projects I maintain a set of local fixes that I regularly rebase on top of the latest code. I don't need to run a bisect on those.

I've also managed other projects/branches like you have, merging the changes into my work.

I also use the cherry picking feature (which rebase builds on) a lot. That is for things like creating hot fixes, pulling in some upstream patches to my local fixes, reordering a branch, etc.