I can offer up my experience with a 25 year old can that I inherited from my father. Seems no one else in the family is interested in camping and this can, which was purchased in the early 70s lived on a shelf in my folks garage for almost two decades.
When my father passed away, I inherited it. In the mid 90s I bought a Whisperlite Internationale to replace an old butane cartridge stove I had. In less time than it takes to talk about it, the stove was completely gummed up and burning very badly. I got sporadic flames. Lucky for me I had an Esbit stove as a backup lest it would have been a very cold and miserable wet night in the Pacific Northwest.
I don't know for sure how long the stuff lasts, but having a can around for four or five years hasn't caused any issues. I do tend to buy smaller cans these days, knowing they will eventually deteriorate after opening.