It is viable for quite some time as long as you keep it cold. Yes, feeding them will help keep them alive, but if it is really a ton of yeast, you'll have to feed them a lot. Tell us more: how much yeast? What do you hope to do with them?
I've got about 1/4 quart of sedimented yeast in a quart growler it is the wyeast strain Thames valley I'm not sure of the number. I'm not looking to culture the yeast and keep it a long time. I really just want 2 be sure that the yeast will be alive in 2 weeks when I go 2 brew my next batch
yeah just warm the jar up to room temp make a starter and pitch them in. Depending on what method (decant or full pitch) make the starter 2 or 1 day before brewing.Some might say you don't even need a starter if they are that fresh but to be on the safe side id make one. If i where you id sweet talk the brewmaster into giving me some of all their strains free yeast is the best kind. Or better yet letting you brew on their system!!
With 1/4 quart (a cup), it sounds like you have about the right amount to pitch into a 5 gallon beer. After two weeks, you should still have enough. Any longer than a month and you'll need to make a starter.