How long will my yeast last?

[bajarob]

Something came up and I may have to put off a brew for a few weeks and I already bought a liquid Hefeweizen vile. It's in my fridge. So how long can I put this off to without it loosing it's umf?

 

[zachattack]

The viability declines slowly with time, but a few weeks isn't that big of a deal. What's the date on the vial? You can check Jamil's site (mrmalty.com) to determine the viability and see if you'll need a starter.

 

[kapbrew13]

I believe I read on another post, year old yeast worked. Just make a starter. Right?

 

[zachattack]

The viability is the percentage of yeast that are still alive. Ex at 100% you have 100 billion cells, at 80% you have 80 billion cells, etc. In theory as long as you have a few live cells you can always build them up in a starter to get more.