A good question- I can say yes to 20/4!
I bought a small UFO LED, that outlined the 12/12 and 18/6 schedules.
The unit had a tag on it said not to operate more than 10 hrs a day.
It's been running 20/4 for a couple of months now, without issue.
The other 3 LEDs did not come with a 10hr/day warning.