Quote:
any of the stamps I would not put in my own collection...missing perfs,dirty cancel, crease etc; perish between my thumb and forefinger
Then please stop!
Even if you are absolutely certain that you are not destroying some hitherto unknown variety, and you are equally sure that the postmark is not one that would be of interest to a postmark specialist, then consider giving them to a young person who just might start collecting, a teacher who just might start using them to illustrate a teaching point, or a charity which can always use any but the most seriously damaged specimens to make up kiloware.
The more stamps, however grotty, that you destroy, the more you lessen the chance of another collector making a discovery.