Stopping time strategies

I'm the non-ADHD spouse and my husband was diagnosed about 3 yrs ago.  He has gone through phases of being great about being willing to work on adhd issues/develop systems that help him alternating with periods where it seems as if he has forgotten that the ADHD is even there, and resents it being brought up by me.  He is on medications, but likely not the optimal regimen for him as he doesn't seem to get much effect from it (he's working on this with his doctor).

One issue we have that I haven't seen addressed elsewhere in this forum is how to help the ADHD spouse pick a good stopping time from an activity and stick to it.  I realize that hyper focusing is ultimately not a good thing, but after days of him not being able to get started/get things done that he has committed to doing if he does get hyper focused he has a hard time stopping which usually ends up burning him out which leads to the next week being wasted!  I have to admit that I appreciate it when he is able to get things done as well, so when he is 'on a roll' part of me doesn't want him to stop either, as I know that even if he does stop at a decent time to get rest there is no guarantee that tomorrow he will be able to get going again.  We have tried making lists of jobs with times associated with them with the idea that he would set an alarm for that amount of time when starting the activity so he would be reminded to stop, but although he agrees to this in principle he hasn't been able to execute it.

This is particularly a problem right now as he is in school and has the summers off, so there is no external structure to help keep him on task.  I work full time and it is frustrating for me to go to work all day, come home and have him there having done nothing all day, and still have to clean up after him, make dinner etc (because he wouldn't 'see' that the kitchen was dirty so he wouldn't think to clean it.