People that want to SELL you onion seed every year will tell you that. ;)
Rule of thumb: The smaller the seed, the longer the viability.
‘Empress of Dirt’ says 1 to 2 years for onion seeds. Longer, but you ‘MAY’ have less that germinate, so plant 3 seeds instead of 2 with older onion seed. I’m sure they ‘average’ all of this out because not everyone has optimal storage and/or seed starting capabilities.
https://empressofdirt.net/seed-viability-chart/
Old Farmers’ Almanac: https://www.farmersalmanac.com/seeds-garden-viable
Again, call the company to find out when they’ll be shipping 2025 seed. Any reputable company will gladly answer your questions, I’m sure. :)
IIRC, I’ve been finding almost everything I need at Johnny’s. I’m sure they can tell me that.
The problem this year is not wanting to wait to buy seeds because of the uncertainty of the whole situation in the US.
I’d rather order them now and be sure to have them than not and be screwed. Plus, I’ll have fresh seed viable for more years out by replenishing now as opposed to what I have now.
As far as the onion seeds, I had some of the Rossa di Milano’s that were two years old and figured I had nothing to lose planting them so sowed heavily and almost all came up. I was thrilled to see that.