I only bought expensive 3.5 disks in the 80s and all single sided (720) ones: i have 5 big boxes with them and most have a hole in them; I tried them all a few

I only bought expensive 3.5 disks in the 80s and all single sided (720) ones: i have 5 big boxes with them and most have a hole in them; I tried them all a few months ago and almost all still fully work.