Im using PPG DBC hugger orange with DT870 and it says that there is no pot life but it just needs thourough mixing when reused. Do I have too have it completely air tight or is a little air ok. I was thinking of putting a ziploc bag over the container and putting a rubber band around it, just curious if that will work. I will use it in a couple of days.

DBC is good forever as long as its sealed AIRTIGHT.
Having the lid craked open is bad idea and if am not mistaken agaisnt the law in some VOC regulated areas. Plus when you go to shake it and dont see that the lid is not fully tighted, paint likes to fly all over the place. Ending up on your clothes, the wall and if you're lucky a customer's car graemlins/clonk.gif

Just make sure the lid is firmly pressed down, using a plastic bag is overkill.

consider another factor. Temperature. I have mixed epoxy paints and put the day's leftovers in the fridge and shot them the next day with good results.

Epoxy and basecoat is like comparing apples to oranges! Basecoat has NO potlife(unless you activate it) were epoxy does a potlife.