what specifically is dangerous about out of date flares?

[Gk 66]

I keep a pair of welding gauntlets n my flare box.

 

[nigelmercier]

... I always find it strange that outdoor shops dont sell smoke flairs ...

They do: http://www.outdoorgb.com/c/distress_flares_pyrotechnics/ you just have to spell it right!

 

[Daydream believer]

There's some sense in that and I'm thinking of dumping mine when they become time expired. I don't know how many times they have actually been used to save lives but I suspect that it is very rare.

Well if they have been used once already then you may as well dump them now