Richard -
 
yes, you can safely use the equipment again.  When
the bees leave, the remaining parasites can not survive.
In fact, it is likely that most of the mites left with the
bees.
My experience is that the strips do work, but they only control
and not eliminate the mites.  Be careful to remove the strips
will before your honey flow.  Then treat them again before
the next season.
As for your varoa resistant bee, a few claims have been
made, but I think the jury is still out.  I tend to think
we will find varroa resistant bees from those domestic
bees that survive... I wonder about the need (wisdom?) of
chasing to other countries for breeding stock.  Time will
tell.  There is a continuum of related info in the ABJ and
Gleenings.  If you don't already subscribe, it would be a
good investment.
 
Larry Krengel
Marengo, IL