Hi Pomme,
Keeping your seeds in a cool dry location is best. Some people store them in the freezer in jars or in the fridge. I don't personally do this, I have a cool closet. I do know that if you store them in the freezer, you need to let the container come to room temperature before opening.
Kept in a cool dry location tomato seeds will keep very well for at least 5 years and up to 10. After 5 years, you will still get germination just not at a really high percentage. I'm assuming cucumbers are the same. I know Brassica family seeds last awhile and Swiss Chard does too. I know Ipomoea seeds last a very long time. I don't have experience with the others.
Remy

I would be careful about freezing seeds. I don't believe the Impatiens or Morning Glories will be viable after freezing, at least that is my experience. I have very good luck with just allowing seed to dry on a paper plate. I put them in envelopes and then in a plastic shoebox with a desiccant package, a cool dark place and that's it.

Good Luck, Jan

I put mine in a cool, dark place also. I have read a lot of people store their seeds in the refrigerator, not necessarily the freezer. The freezer may be ok for storage of seeds that require that kind of stratification treatment prior to planting. I do not believe the seeds you mention require that, but you can investigate that further.

Thank you so very much! I want to be able to hold off until i get out of college (possibly 2 - 4 years). I can alway harvest more of the impatiens be rpollinating. The flowers. I willtry to follow your guilines and storn some in the refrigerator and see how that goes. I'll see what does best in the fridge/freezer.