Hey man, it sort of depends on your paint. I had Evil paint stored for more than 6 months. When I used it it shot like it was still new. I also have some Blaze that's over 2 months old now and I still shoot it from time to time and it works well too!
Also, if your storing paint in pods make sure you don't TOTALY fill the pods. Because when you shut the lid and press down on the balls you'll be pressing on the balls and they will become slightly deformed.