How long does it take you to get back into a project after a few days away?

> Nothing told me why I was changing it

That arguably belongs in the commit messages or, in some cases, in code comments.

> or what I was planning next.

That arguably belongs in ./TODO or, in some cases, code comments.

Edit: TODOs in code comments obviously don't have a natural ordering, but i frequently look at diffs to help figure that part out, as they clearly mark the new/recent TODOs.

> Is there anything that actually works, or do you just accept the tax?

There will always be a tax for context switching - even brief interruptions during concentrated work often require longer than the interruption to get back into the work (that's a well-studied phenomenon, actually). There is no avoiding that unless, perhaps, one has eidetic memory (in which case the cost is _presumably_ low enough to be considered negligible (but perhaps someone with eidetic memory can enlighten us on that)).

> How long does it realistically take you to resume a project after 3+ days?

That depends entirely on the project and its complexity/scope. It might be 5 minutes, it might be half a day. i'll admit that i sometimes (okay, okay: often!) avoid going back to something i'd _like_ to work on because i know in advance that this tax is likely to be paid by an inordinately large portion of my current energy levels, leaving little for the actual work. Frequently, though, when _finally_ getting back, i discover that the tax is less than anticipated. Maybe that's an age/experience thing, though - refamiliarizing myself with older code seems to come more easily to me with age, for reasons beyond my ken.