It's a funny story about my Michigan driving licence...
When we lived there you had to renew your licence every four years, but every eight years you had to take the written test just to show you were still conscious. The year after we moved to England I needed to renew but not take the test. I no longer had a Michigan address so I asked a friend if I could use her address and have her mail it to me. She did, and a week later our house was burgled and my bag and everything in it was stolen. I couldn't bear to ask my friend to go through the whole thing again. (And I had a feeling it would involve a lot of questions from the DMV people and my overseas address might cause problems.) I just didn't want to deal with it at the time!
Last year would have been the four year renewal again but I would have had to take the written test. In Michigan.
I suppose I should just do what's needed to get myself a California driver's licence since I go back there every year to visit my family and it would be easy enough to take any periodic written tests, use a relative's address, etc.
I don't remember the California road test being that easy. I flunked the first time, but that was back in the 70s...
Thanks for doing that research, Aimless!