We use the same color without hardner and our pot has an air controlled mixer inside. When ya come in, turn on the mixer and she is ready. Sucks though, we have about 10' of hose, it will separate out sitting so you have to waste some until it run color again.I never tried leaving the paint in the pot. No different than in the bucket.
We also keep about 10 different colors on hand and everything gets primer as well.