I live in a hot 'n humid saline coastal environment, play every day and my hands sweat salt 'n acid. Fortunately the entire house including my music studio where the instruments are stored is air conditioned. Regardless, on the guitars which are being played daily, even though I apply Dunlop Formula 65 Ultraglide String Conditioner before and after playing, uncoated metal strings will have oxidised and turned completely black within 6 to 8 weeks.

Every bulk pack I've bought brand regardless contains 10 sets rather than 12. I'd easily consume those within 3/4 of a year restringing just two guitars, and as I have more than two, the immediately to hand convenience and massive cost saving in buying multiple packs makes practical as well as economic sense for me.

Don't know I'd subscribe to the, paraphrased, 'gone bad in 12 months' theory. They are't bananas or tomatoes. D'Addario refer to their static bag enclosures as "corrosion resistant packaging" the strings within treated with "VCI corrosion protection". No, they're not vacum packed, but they are treated with corrosion inhibitor and each set is individually heat sealed in the bag from moisture and other contaminants. Deterioration over a twelve month shelf life? Arguably insignificant.

Ultimately, sensible purchase volume certainly depends upon individual application and string changing routine. How frequently one changes strings, including how many guitars one might concurrently have using that gauge of string. Bulk works for me.