Storing seeds for long time
The most important advice about storing seeds for several years is - DON'T! Seeds are meant to be planted and not stored.
Seeds are they way plant’s mechanism for propagation and survival. They normally last one or two winters in the soil, and wait for the right condition to germinate. This is what Nature intends for them. If you leave them in your shed or garage, the fluctuating temperature and humidity shortens their life. The longer they stay, the less of them will germinate.
Most food plant seeds last a few years. Some non-food seeds may last longer. Storing them properly will extend their potential to 3 or more years.
Buying from a store
When buying from a local store, make sure you find the year indicated on the package. If you do not find it ask the staff. Do not assume they are from last year. Businesses cheat so they do not lose money.
Please do not throw your seeds once they stay more than a year or two. Try them and see what comes out. Some of the seeds are more resilient to droughts or temperature. It is just that the chance decreases with the time.
What we do
We keep our seeds at stable temperature and humidity. We store them in thick plastic bags to preserve the humidity. We keep them in dark places, away from the sun or artificial light.
Some times we freeze them to make them last a few years longer. Yes, freezing them is normal, but those are not the ones we sell. Several "Doomsday vaults" keep seeds frozen. Your freezer is a good option too. You don't open and close it often and its environment is stable.
The ones we sell
We sell seeds from the same or previous season only. We rarely keep older ones unless there was an issue with the harvest from the current year. We clearly mark the packages with the year of harvest. This way you can plant them next spring or even sooner when growing the plants inside your home.