Re: 5/8 gone
Thought losing bees was accepted as part of the TF plan. Then you have to rebuild from mite tolerant ones, until (hopefully), you end up with bees that will be OK. But you'll still always likely have losses bigger than if you treated.
At least I guess, losing hives through winter like yours, the hives are unlikely to get robbed and therefore not spread mites to the other hives.
44 years, been commercial, outfits up to 4000 hives, now 120 hives and 200 nucs as a hobby, selling bees. T (mostly).