I'm not knowledgeable about strings at all, but I did use D'Addario strings.

However I have just passed my guitar onto my grandson who's making a decent go of it but I also gave hime some packs of D'Addario strings that I've had kicking about since I stopped performing.

How badly do the strings deteriorate with time, if unused and still packaged? Would I better to get the lad to chuck them away and buy him new ones?

I must admit that the strings that were on the guitar didn't sound all that bad when I dug the guitar out of it's case to pass it on, but perhaps that's just my ears deteriorating like the rest of me'

BB