As long as you store them in a low humidity spot, they should be OK. A year or even isn't really a long time for strings still it the package.

The ones in a sealed pack like Daddario and Ernie Ball should last many years on the shelf. I've opened strings that came in a shrink wrapped box and found them to have rust spots. The strings were in the box in envelopes, so they weren't sealed in any way.

If you google the subject, you'll find people so believe they will become dull over time unless they are stored layed our rather then wound in a circle. There's lot of skepticism about this though.