With onions, if you start them from seeds, you need to buy new seeds every year. Onion seeds have a very high failure rate, this applies to green onions / scallions as well as the larger onions like whites, yellows or reds (all of which you can buy as sets aka small bulbs which usually do better than seeds) With cucumbers, they’re a warmer weather later in the season seed/planting so it might be smarter to either start them yourself in a green house then transplant any seedlings to the garden and/or buy seedlings from someone who did the work of sprouting the seeds for you & plant those instead. If you have a seedling kit with a heat mat, so much the better. I would also start tomatoes & peppers this way or buy seedlings already sprouted & ready for transplanting. I’m not a big enough fan of sweet corn to bother planting it myself, it takes up a lot of space in a garden plus it often has lots of issues with pests (bugs, worms, gophers, racoons) & other diseases like smut/fungus. It’s something I just buy from others locally who are better at growing it than I am & since it’s not my favorite, it’s not a must-grow myself thing. Generally you want to keep your stored seeds cool, out of the light & at the right moisture levels. I don’t know that the prepper/survival seed vaults are any better at extending the life of your seeds than seeds you buy & store carefully yourself, I’ve never tried them out. There are great books on seed saving & preserving worth investing in if you are seriously gardening. I have a stove top Presto pressure canner I love, but it’s cool to see there’s also an electric version out there to try now. I’ve hacked an electric turkey fryer to use as a waterbath canner, it works brilliantly for tomatoes & high acid pickles, I can process more jars at a time than in my stove top waterbath canner.