Welcome to the list Judy.

If it's propane, unless your tanks are rusting out from under it, it's fine. If it's in a climate controlled area, dry, and you don't crack the seals, it will be as "propany" five years from now as it was yesterday. Like fruit cake, so long as it is kept in a sealed container it won't disappear, and unlike fruit cake, it never gets stale.

For reference, I've seen unopened colman cylinders that have been in storage for ten years work fine. And while they were stored out of the rain and snow, they weren't stored anyplace heated. But I wouldn't make a habit of it.