All things considered, I will say it again, keeping the mite count very low is number one in keeping bees healthy.
While examining our hives in Florida during this last spring, we discovered one yard of 80 hives that went without any mite treatments and had a high varroa mite load. An ether roll of 16 mites was common.
I took the yard of 80 hives from a 16 mite ether roll to almost zero with 3 treatments with oxalic. Both deeps (doubles)were treated each time with 25 ml, more or less, for a total of 50 ml per hive. I would generally be able to treat 80 hives per gallon. This is a spring treatment with lots of new hatch.
On the last treatment, I gave each deep (doubles)50 ml of 3.5%. That is about 100 ml per hive. NO damage. That's 40 hives to one gallon on the last treatment. I must point out that there was a constant hatch of new bees coming in and also nectar coming in daily.
After hearing so many stories of beekeepers hurting their bees with too much formic, thymol, oxalic, fuji mite, etc., I would like to make a recommendation to all beeks. Trial every new treatment on a few hives before treating all your hives. Test each treatment according to conditions like temp, nectar flow, population, etc. Put a sticky board on the bottom on the trials. You may need more or less treatment. Conditions can vary greatly.
Then roll roll roll.
Or shake shake shake. ;-)