Eh, I imagine over a period of time/ climactic changes they might develop *some* natural corrosion, based solely on the materials used and all that, but over the long term, I can't imagine the change would super-drastic.
I've seen some stores that have had the same packs of some off-brand or pricey strings on the rack for a couple years at a time and they don't seem overly concerned about it...so I'd think you're fine....
UNless you're the type to only change strings once a decade....
