Does using fresh seed really matter?

Maybe it really does, as some of you know I like my onions and started sowing seed just after Christmas. My Kelsaes and Ailsa Craigs (fresh seed) have germinated well with almost a 100% success rate, my year older Mammoth seed on the otherhand has failed to germinate all bar one seedling.
I'm not too bothered about that cos I only sowed the mammoths cos I had some seed left BUT I'm hoping to sow some older seed for varieties I DO want to grow.

Not just onions either :(

 

I think its pretty well known fact that some seed keeps longer than others, I also have grown very old tomato seed, but some seed only lasts a year or two at best.

I think its always best to use the freshest seed you can, but no harm in trying older stuff, just dont rely on it.

If your keeping seed from one year to another, dont keep it in the greenhouse, you need somewhere cool and dry.
Some might say the fridge but I think that can get a bit damp.

 

As JWK states, seeds lose there viability with age.

This can be extended with good storage, but in most cases , you are better off buying fresh seeds i.e. Parsnip (Hollow Crown ) 50p for 500 seeds.

Some will store better than others, and trial and error is how most people find this out.

Surely it's best to work out how much you saved on your previous crops that you didn't need to buy from the supermarket, then think of the cost of getting poor crops from old seeds.

I put away a quid each week to pay for the following seasons crop seeds, and I always have some change for a pint or two!

 

All good advice above.

I've found lettuce and leek seeds to keep particularly well but like everyone says, you have to give them a chance by keeping them somewhere cool, dark and dry.

 

Thanks all, probably my own fault as the old seed was for a while stored in a biscuit tin in the greenhouse :( . Seed is now being stored in a cool, dry, dis-used coal cellar