".... difficult and slow to start Vitis Riparia plants from seed" Noxious weed is some areas, prohibited in Ohio. May be injurious to nearby trees and shrubs if not controlled. It doesn't sound like scarifying would be especially helpful, or soaking either. They do need to be stratified, the chill must be moist to be helpful, dry storage in the refrigerator is only storage - the key is the moisture. Plants for a future database: "Seed - best sown in a cold frame as soon as it is ripe. Six weeks cold stratification improves the germination rate, and so stored seed is best sown in a cold frame as soon as it is obtained. Germination should take place in the first spring, but sometimes takes another 12 months. Prick out the seedlings into individual pots when they are large enough to handle and grow them on in a cold frame for their first winter. Plant out in early summer."

Swallowtail Garden Seeds website: "Kept at 65-70 F., germination is in 21-30 days. Seedlings are fragile and must be handled with care." I've winter sowed them and summer sowed them--great germination either way. They're late to come up in the spring, so mark where you planted them. This year I laid down cardboard & mulch over top of them by mistake. A couple of weeks later the mulch kept rising up higher and higher. When I looked to see what was going on, I saw my oldest clump of balloon flower coming up under it. They have a long taproot and resent being disturbed so plant them where you want them. That being said, I dug mine up from my old house and brought them here 5 years ago and they never missed a beat. My blue ones get pretty tall and flop over so I usually whack them down to about 8-10" the last week of May. They stay in a compact clump and produce lots more flowers that way.

I can't answer the question about older seeds, but I can give you a little info about my experience this year. I sowed a couple dozen butterfly weed seeds (I got them from Prairie Moon) this winter (mid February) in milk jugs. About half of them germinated. I transplanted them into small pots after the second true leaf emerged. They were tiny at this point, and I think it was perhaps early May by then as we had had a longer winter than usual. Not long after that I moved them into the garden. I was a little worried that if I left them in containers too long I'd damage the taproot when moving them. Around the same time I planted a couple of larger ones I'd purchased in containers from a nursery. One of these died about a month later, and the other looks anemic compared to the ones I wintersowed. The wintersown seedlings grew slowly until late June or so and have been doing well since then. Most of them have two or three main stems that have been bent down quite a bit by winds (possibly the soil is too rich as well). I've propped a few of them up with stones. I was surprised that some of them are flowering now in their first year. The attached photo was taken this morning.

Studies to determine the length of time and the conditions needed for successful stratification are common. Many types of seed have been studies extensively and conditions are well determined. Some rarer types may not have had much study. For the most part, those stratification requirements you see are probably based on one of those studies. If 5% of some type of seed germinates without stratification, 20% germinates after 2 months,......and 95% germinate after 4 months, you will probably see recommendations for 120 day stratification. In some cases, the lengths may be guesses. If seeds require stratification and you don't provide sufficient time for that process, much of the seed will not undergo the physical and chemical changes necessary to break dormancy.