Probably not. Or at least not for long-term storage.
Yeast
While dried yeast is designed to be shelf-stable in its original packaging, once it has been opened, it’s vulnerable to air, moisture and heat. For long-term storage, the best place for your yeast is in an airtight container in the freezer. According to Red Star Yeast, it will stay fresh for 6 months in the freezer, but in practice it can last longer.
But putting yeast in the freezer has its pitfalls. For one thing, every time you open the very cold container, you’re introducing moisture, which isn’t good. And yeast is vulnerable to thermal shock, so if you take a spoon full of frozen yeast and add it to warm water to proof it, you could kill off a whole lot of yeast before it has a chance to shake off the cold and wake up. Letting your yeast warm up a bit before adding it to warm water is a good idea, and it warms up faster if you keep some in a slightly less frigid environment.
I use a two-step approach to storing yeast, and it hasn’t failed me yet. I keep the bulk of the yeast in the freezer, tightly sealed, and I keep a smaller container in the refrigerator. When the jar in the refrigerator is empty, I refill from the freezer. When I was being even more particular, I used to vacuum seal the yeast stored in the freezer. That’s a good idea if you buy in bulk, but use the yeast slowly. I use it fast enough, so even though I buy a pound or two at a time, I no longer bother with the vacuum sealing.
According to Red Star Yeast, refrigerated yeast has a shelf life of 4 months, but I’d suggest keeping about a month’s worth in the refrigerator and keeping the rest in the freezer.
If you ever use fresh yeast, your best bet is to buy it and use it as quickly as possible. However, sometimes I buy fresh yeast in bulk, and there’s no way to use it fast enough. In that case, I cut it into cubes, wrap it tightly, and store it in the freezer. I find that it takes about twice as much of the frozen yeast in place of fresh yeast. But of course, always proof fresh yeast. The shelf life is so short, there’s a chance it was dead when you got it.
If you have sourdough starter, the best place to store it when you’re not interacting with it is in the refrigerator. I’ve seen suggestions that it’s good for a week or a month while refrigerated, but in practice, I’ve let starters languish in the refrigerator for three months and have been able to revive them. Needless to say, it takes a couple days of feeding to get a starter of that age to spring back to life, but it’s not hopeless unless it has other things growing in there. A coat of fur is not a good sign.
Sourdough starters can also be dried for long-term storage. Personally, I’ve never done that, but I have revived dried starters I’ve gotten from other sources. You can store your dried starter in the freezer for extra protection.
Flour
When it comes to flour, refined white flour will last for a fairly long time at room temperature, but any whole grain – whether it’s wheat, oats, rye, or any specialty grain – can go rancid because of the oil in the germ. Believe me, rancid flour doesn’t get any better when it’s baked into bread or cakes or cookies.
Of course, you should keep your flour and other grain products tightly sealed to avoid infestation by hungry crawly creatures, but another consideration is ease of access. I’ve seen really pretty canister sets with loose-fitting narrow tops, and thought that whoever designed them must not cook a lot. A better design is something that seals tightly and that allows you to fill your measuring cup easily, without spilling flour all over your counters. Or, if you measure by weight instead of volume, you want easy access for whatever scoop you use to dispense the flour. For my ease of use, I leave a measuring cup and a small scoop in my flour canisters, so I can scoop large amounts with the cup and small amounts with the scoop.
When it comes to finding a place to store those canisters, colder is better. But of course, it depends on storage space and on how fast you use the product. For flours that I use often, I keep them at room temperature because there’s no time for them to go bad. For flours that I use less often, I store in the refrigerator or the freezer, depending on space available and on how often I use them. But even with white flour, when I buy in bulk I keep what I’ll use right away in my easily accessible canister, and store the rest in the refrigerator, tightly sealed.