"Ideal storage conditions" are debatable and there is lots of info here on proper storage including a FAQ. Generally as long as the seeds are not exposed to heat or humidity they are fine and will remain viable for many years.

Plastic seals in humidity unless the seeds are essentially bone dry or desiccants are packed with them so paper is more recommended and cooler is better.

There are a few exceptions - primarily allium family - but otherwise a better than 50-60% viability is assured for years.

Dave

20 years holding bachelor buttons? In the dark, cool, in their envelopes?

I've got 5 year old seeds that germinated this year. Not 100%

Not sure where the 20 years figure came from. But in their original envelopes kept dry and relatively cool they'll last several years.

Rodney

i acquired the seeds 20 years ago. the date on the package was 1995. :)