Can auto-paint be left in a sealed spray gun reservoir?

Background

I’ve decided to try my hand at repainting the damaged area on my ground effects, mostly just to be able to learn something fun and new. That means lots of mistakes incoming, but I’m trying to head off what ones I can.

Question

I’m going to be using my old Earlex Spraystation, which uses this cup. I ordered a new cup & cap just to make sure the lacquer / poly I’ve sprayed in the past and gotten stuck in the cup doesn’t flake or interfere in some other way.

When I spray I’m sure I’ll have leftover base coat in the cup. I’m hesitant about pouring this back into the can, and was wondering if I could just pull off the cup, put the cap on, and store it like that until I used it again. Same goes for the clearcoat. I expect I will be spraying on and off for just a couple of months; I don’t need the paint to stay good beyond the summer.

I will, of course, clean the rest of the gun thoroughly before storage.

Why

There are a few reasons this seems preferable to me:

• Pouring something back into a can can introduce contaminants, from dust to pollen to bugs. I guess there won’t be too terribly much of a chance of this with the sprayer being sealed, but it seems like one extra unnecessary point of failure. If something does go wrong and the paint in the cup is bad, I’d rather not lose the rest of my paint as well.
• Having the paint already in the cup makes it easier to pop on without having to worry about opening a can and pouring (which requires a tarp or mat…or cleanup)
• Being able to just reuse the cup for 2-3 sessions reduces the times I need to open the can and allow contaminants and fresh air in.