Shelf life on grass seeds?

I was about to start a thread about how my overseeding was not working because the seeds are not germinating but I can see other members have very similar issues so I'll heed the advice given in those threads instead.

However, I am wondering if there's an expiry date on the seeds themselves and/or the way they're stored overtime and that could that be the reason why.

I had a box of Evergreen Multi Purpose which I used for the overseeding. The batch date on the bottom says Feb 18. I bought it in April that year and stored it in a shed since then.

I cannot see any seeds whatsoever germinating. The places that suffer the most do not get as much sun and the soil always seems to be damp when other (better) areas look as if they need watering.

Thanks very much.

 

I've found that grass seed only seems to be completely viable in the first year. The second year I only get germination on about half no matter who has produced it, or whether it's stored as John has suggested.

 

Yes, I fear they're no longer 'active'.
I think I'll have another go with new seeds.
Can anyone recommend a type?
I would say it needs to be a hardy one that can grow in less than ideal conditions.

Thanks for all your help.