That’s okay, we can ask Ee to do it
More seriously, I see it as an extension of what is already done checking for active voters: email new inactive people to check if they wish to remain active for voting. At the same time, we would do a similar thing for active committers: email new inactive people to check if they wish to remain active for committing.
My suggestion is to check yearly, and use the same “no commits in 2 years” to trigger inactive. Partly for clarity, to mirror the inactive voters process; partly for practical reasons, to make it easier to administer.