Some expire quickly (ie parsnip), others can still germinate after several years. There have been reports of seeds from Egyptian tombs that have sprouted!! So, they are always worth a try. Good luck!

yes!!! I tried growing some pea seeds that were 2004 lol Well I had to try didn't I they didnt grow lol Volunteer is right thought. Always try thats my moto

It largely depends on how they were stored. This year I bought quite a few seeds from large stores (should have known better!) including things like peas and beans which normally keep for years and germinate well. Two thirds never came up, and I guess they'd been stored in temperatures going from cold to hot and back again in the shops.
When you store seed at home put them in a jar with some moisture absorbing gel and put the jar in a fridge; that way they will keep for ages.
Tomato seeds lasts for years, while as Volunteer says, many root crops (umbellifers like parsnip, carrot etc) don't keep their vitality.
I think the Egyptian tombs thing was a myth, unfortunately.
Even in the professional seed banks which have been set up, they need to resow and regrow the seed from time to time to keep the stocks fresh.

Thank you all for your comments, I will have to wait and see in a few weeks.

I have had flower seeds pass their use by date and they have come up lovely.And they were about 3 years out of date

Many thanks guys, I think some are starting to appear.