I grow a LOT of plants in pots.
I love their versatility and the way they can add height and colour to any spot. The only thing I don’t enjoy about growing plants in pots is having to empty the soil out of them in the fall. And because I live in a climate with winter and I grow plants in breakable pots–terra cotta and ceramic–I do have to empty them out. Otherwise the frost will get to them and they’ll crack…and I’ll have to buy all new pots next spring.
Plastic pots are prone to cracking like this as well, although your odds of them surviving are better. I have overwinterd a couple hostas in black plastic pots that some of my trees came in, and they seem to do just fine. I also feel confident leaving soil in my pots made out of recycled tires, and in my cast iron urn.
You can buy frost-proof pots, usually made out of a material like fibreglass but they’re quite a bit more expensive than your average pot.
Once empty, I either haul them into the garage (a wheeled dolly was one of my smartest purchases) or shed, or leave them outside when I run out of room in those places. The trick to storing them outside is to turn them upside down and then put a stick or something under at least one side, so that they don’t freeze solidly to the ground, as that can cause them to crack. Someone explained the science of this to me once (something about the stick “breaking the hydrostatic connection”) which I didn’t really understand, but it works.
I have managed to overwinter this particular red pot when it was full of soil, once, by turning it upside down and leaving a stick under one edge. I didn’t intend to leave soil in it, but I was ill that fall and the soil froze solid in the pot before I was able to empty it. I put a stick under it, hoped for the best, and, to my relief, the pot was still fine in the spring.
If you want to be really careful with your pots, after you empty them you could put them up on 2 x 4’s and even cover them, as drier is better. I confess that I don’t do this myself, but I can see where it’s good practice.
For really large pots that you aren’t able to move, your best bet is to clear as much of the soil out as you can and then cover them over tightly with plastic or something that will keep moisture out. I don’t have pots so large that I’ve had to try this myself, but I understand from reputable sources that it works.
Potting soil is really only “good” for one growing season–by the end of the growing season it has usually lost most of its nutrients and its structure has broken down. It can be revived by adding compost, etc. but it’s best to get it out of your individual pots and into something larger that you can mix in anyway.
All of the soil that I take out of my pots gets put to other uses in my garden, including as insulation for my roses–more on how to do that in a few weeks, once the ground freezes (it’s too early to winterize your roses until the ground freezes). Until then, I’ll be storing my used potting soil in some big trugs and bags.