We join in a seed swap every Feb. with an online group, we usually have it at a restaurant in a small private room. It's always good fun the shed winter for a day and gather with friends and fellow gardeners. Many have heirlooms they have collected and share. The only heirloom I save and share is Limbaugh's Legacy Potato Top tomato. I usually ferment my seeds, and get a great germination rate using this method. We take turns hosting plant swaps in May and Sept. so quite a few heirloom plants get passed around at those meets also.
Talking about desiccants, couldn't you use water crystals to reduce moisture in your seed storage containers? I almost always have those on hand for my container soil mixes.