Ask HN: Selling software, how much long-term support should I provide?

I am working on a piece of software for hobbyist that will need to call my server API to work. I am thinking in selling it for a fixed amount - however, I can't promise it will keep working on a few years.

If the software stopped working you woulnd't lose more than what you paid for (imagine it as a newspaper reader, if it stopped working you didn't lose any data, you just cannot use it anymore).

However, since they are paying a fixed price to buy the software, I'd like to make it clear that it won't work forever. Anyone has any suggestions about the wording, terms and conditions, etc?

The other possibility is to make the price yearly, and if they stop paying, it won't work anymore (which keeps me motivated to maintain the API), however, I'd prefer to avoid managing recurring payments and focus on develop the software and just provide a download link after payment.