Is there a data base on the internet that you'd recommend which tells you how long certain seeds are known to remain viable on the average?
Thank you in advance!
There really is no comprehensive list. There are a few vegetable and common flower seed lists. Those are just guides though. I think there are not many lists because there are so many factors involved on the viability of seeds.
Most seeds though last a few years some many years. A few seeds have a very short shelf life.
Spring ephemerals(plants that appear in spring and go dormant by summer like Virginia Bluebells) and some woodland plants like Hellebore tend to have seeds that need to be planted immediately upon ripening or they will never germinate.
Some other plants have seed that need to be sown by the following year or they won't germinate like alliums.
Generally though most flowers and veggies do well for a few years. I have many 3-5 year old seed I sowed this year and had excellent germination.
If you have specific seed you are wondering about, you can always post about that seed. Or if you have enough seed(unless it is seed that needs a cold period) you could do a paper towel germination test.
I hope this helped some,