Repeat of post to previous swap:
This chart on Joegardener.com is one of the most comprehensive I've seen.
Note that it says the dates are for "optimal" storage conditions but it doesn't say if that means optimal as in their suggested way.
They recommend storing dry seeds in a sealed glass jar with a pack of desiccant, in a refrigerator.
Another site said freezing can further extend longevity but the seeds need to be dried below 8% moisture for this, and not all seeds can tolerate being that dry.
Hope you find this useful. I've decided to only offer seeds I've had for 1 year or less, unless the expected longevity is at least 4 years.
Pat
