Is this a good use for old paint?
 

I have all my exterior done in SPI epoxies and primers, but I don't have enough for the bare interior. So I went rummaging through my old supplies and I found a quart of PPG DP74 red oxide epoxy primer plus catalyst and also a half gallon PPG K36 primer plus catalyst. Both of these are something like 8 to 10 yrs old but stir up nicely still. I have heard and read that there is a shelf life of this stuff. So I was thinking it couldn't hurt to shoot this on the interior of the shell since it isn't a critical area.

Is it true that there is a shelf life, and even if so is the interior a good place to use these materials up?

I'd mix a very small ammount and brush it somewhere (no need to dirty the gun) and see if it hardens normally, if so it's fine.

You dont wanna spray the whole batch and find out it won't kick and you have a mess to clean up.