Older Ernie Ball strings that came in paper packaging did go bad within a couple of years, where strings would have visible rust spots. Newer strings (even those not mentioning air-tight packaging) come in a plastic packet, with each string inside a separate paper envelope.
If you buy a set (such as a set of 3, 6, or 12), they usually come in a larger plastic bag with each set in its own separate plastic packet and then each string in its own paper envelope. Many people buy strings in bulk because it's cheaper, and if kept properly, you should expect fresh and corrosion-free strings for your guitar for several years (1-3).
Some slightly expensive Ernie Ball Strings come in Element Shield Packaging, which should keep the strings from corroding even in harsher coastal areas.