Yes, leeks like onions are usually viable for only 1 year. I have found that if I save my own onion and leek seeds they often last 3 or 4 years when stored properly.

I find leeks seeds remain viable longer than onion seed does...decent germination for 2 or 3 years. But they don't last as long as tomatoes, squash, etc. Older seed often takes longer to germinate, though. Yours may show up soon.

My experience is the same as naturegirl's. If kept cool and dry your leek seed germination rate shouldn't lose more than about 20% from what it was the first year. I keep all of ,my seed in doubled up zip lock bags with desiccant packets in my beer fridge though. If your seeds were kept at room temperature and were exposed to humidity fluctuations then you might get the results that you are experiencing.

For me leek seed germination takes 6-14 days with soil temps around 70. If their not up within 2 weeks they probably won't ever sprout.