I have these and can find everything I need to know EXCEPT how long do the seeds remain viable? as I like to save my own localised seeds whenever possible. I would be grateful for any info you have on this.
Read this article about how to preserve seeds and, if you preserve them properly, you may find they'll be viable for quite a long time. How long? Too many variables to venture a guess.
https://www.gardeningknowhow.com/garden-how-to/propagation/seeds/storing-seeds.htm