On my reef tank, I test No3, Po4, and Alk weekly, on the same day. I’ll sometimes test calcium too, but cuz it’s more involved with a Hanna checker, I tent to skip it, especially with corals looking good.
For the FOWLR, i tend to focus more on Po4, testing weekly, on the same day with No3 once at the beginning of the month.
I don’t test the Pico tank, as there’s not a heavy bio load and I do a weekly 50% - 75% water change. I have tested No3 and Po4, but more of a curiosity.
There are times when I get too busy or life in general gets in the way and I can’t test, but typically try to keep a good schedule.