Extending shelf life of two part epoxy chemicals

Folks - I've read where you can stretch the pot life of two part
you've already mixed, but my concern is stretching the shelf life of
the individual chemicals once they are open.

I'd like to begin spraying 2 part over some of my smaller fittings.
I'll also have other parts preped so that if I have extra epoxy, I can
use it up ,. however, I'll still be left with more work to do in
three-six months and now, chemicals on the shelf which have been
exposed to air and probably will start to go downhill.

Anyone have suggestions for stretching the shelf life of the
individual chemicals? - Mike