I've got a drawer full of K&B Super Poxy that has been "aging like a fine wine" since I painted that same airplane. Never even occurred to me it might still be useable. Sounds worth a test shot or two.
As far as I can tell, it has nearly infinite life. My limitation has been thinner, but the Klasskote #550 "fast" thinner appears to work fine. Some varieties and batches of hardware store thinners also work, however, you can never tell from batch to batch, even if they are from the same company, part #, and can.
If you need colors, I have many, but not blue or white. I have all the K&B green or orange you might ever want. Also, a decent supply of the #550 thinner, use all you want but replace it when you get the chance.
Don't use the green over the yellow unless you plan on moving to Australia.
Expect the K&B catalyst to be dark brown to nearly black, even it was unopened. I use that to good effect to sort-of match the yelled white paint on my airplane, but it *will* affect the color, white of course more than most. But of course I have white KlassKote, too (including the can I had to cut open with a can opener after the screw-top decided to become one with the spout). It is *stark white* when used with clear catalyst.
I have freely mixed the KlassKote and K&B catalyst, and that also appears to work (same thing worked with K&B and Hobbypoxy - everything was good except the thinner). The regular Klasskote or Hobbypoxy thinner (#500)
*will not work with K&B* of any variety, it will sort of "curdle".
Brett