I realize this is an old thread. I came upon it when doing a google search on coolant shelf life.
Originally Posted By: The Critic
I believe it's one year, due to additive fall out.
Seems extremely short when you take into account that BMW considers it a lifetime fluid. I know the definition of 'lifetime' is vague, but still. I've got a 5-year-old unopened gallon of this BMW Ethylene glycol-based coolant, and still plan on using it for top ups in my car. I really can't see why not.