This does seem obvious. However, if you treat as per the label, the
> survivors will also be the ones that are resistant and will pass on their
> resistant genes. I don't see why leaving the strips on over winter would
> make any difference whatsoever in the development of resistance.

What we have always been told by makers of chemical strips for treating
varroa mites:

There is always a small amount of chemical left in a strip. Not enough to
use the strip again for the next treatment period. If you leave the strip in
longer than the label treatment time it serves no purpose and exposes the
varroa to very low levels of chemical which helps build resistance.

Bob