When it tells me its had enough, usually too late.

usually first thing in the morning sometimes in the evening if Wifey is taking a long shower

every 30 seconds as of this new years resolution.

When I was young (35 and younger) I would be reckless with my sleep and work all hours. Now that I'm in my 50's, I prioritize taking care of myself (daily little habits) to avoid too much wear & tear/burnout.