Whiteboards have been my main strategy too. And a little while ago I ran across this: https://community.frame.work/t/whiteboard-input-module/58985 and bought the same stickers and pens and it works much better than I expected - the pens write super-durably for dry-erase and light bumping doesn't erase them at all. I have weeks-old reminders on there that are almost new looking.

For day to day stuff I just use a more normal whiteboard that I do my best to erase at the end of the day, and migrate longer term stuff to some other location. I like it better than a regimented "always empty" system since reasonable leakage from one day to the next is pretty common for me.