I keep my seeds in a bin, either in little baggies or in their original envelopes (depending on if I bought them or collected them from our garden). This bin has been upstairs where it's hot and downstairs where it's cool (55-65 deg F). I'm AWFUL with my seeds. Inconsistent temperatures, forgetfulness, etc.
We hadn't had a garden since 2016, but this past summer wanted to grow as much as possible. Most seeds were from 2012 to 2016, and I expected there would be problems germinating such older, poorly kept seeds. So I planted everything (indoor starts), just hoping some of it would germinate. And darn near everything grew. No germination problems whatsoever. Instead of having too few plants to work with, I had too many. Carrots, lettuce, melons, pumpkins, tomatoes, peas, beans, herbs, sunflowers - even field corn. The only things I needed new were sweet corn and potatoes.
So in my experience, seeds can be fairly forgiving. I wouldn't suggest banking on that, but it does take some pressure off in my mind. I'm thinking from here on out, if I keep seeds consistently cool in the basement (preferably in air-tight jars with those little anti-moisture thingies?), I should stand a pretty good chance of being able to keep them viable for quite a few years.