popped 2 6 minute orange smokes out here last year, dated 1986!
both worked, it was a still evening and it all descended down to the bottom of the village and filled it with a nice orange fug for ages! the locals were very confused for ages
I would buy a flare pack in year one, then each year add a few extras individually, that way plenty of flares, with differing batches and expiry dates (incase there's a duff batch) and always have a full set of in date ones, without the expense of a full flare pack
the ones that were upto just a few years out of date always stayed on the boat as a backup, who cares about expiry dates when your sinking and the more pyros the better IMHO in date or not