as long as its stored in the correct temperature in the dry and the bags are turned regular, should be good for a while, i think paint has a shelf life but not sure what it is tho
On a training day last year I took all the old paint I could find laying around in my storage area..mostly tourney leftovers half bags etc all different brands and colours about 10,000 balls in all ...it had all been kept in closed bags and turned occasionally and I rekon the oldest paint was 3-4 years old and it all worked perfectly..in fact quite a lot of it had been complete gash when it was fresh but had definately improved with age.
Also went down well with the Missus as apparently paintball kit can take over the house if its not culled every so often