Most sources will tell you not to reuse potting soil. That said I and many others that I know of do reuse it for at least a second year. I just leave it in the pots outside. In the spring I dump into a wheelbarrow or onto a tarp mix some new potting soil with it and refill the pots.

Thank you for the information! After the second year, what do you do with the soil? Is there a way to enrich the soil again, so I can keep using it, for example, by adding compost? Didn't really realize that I couldn't use the soil for more than a year or two, so this is a surprise! Since soil is not cheap - and heavy to carry - and not much space to dispose of, wondering if there is a way to use for longer term. Is this only for organic soil, or do you not reuse any soil for more than a year or two?

You could probably go longer if you refresh it with compost. The problem with reusing any potting mix is that the organic components break down and you lose the airspace in the soil. Your best bet is to try it and see what happens. I add mine to my compost pile or my flower beds. I also pot up a lot of plants for my garden club plant sale and since these plants are only going to be potted up for a week or two I use some of the old potting mix to pot these plants.