Developers are entitled to earn more money when they continue working. On the other hand, it is unfair how consumers have frequently needed to re-purchase products that they bought with the impression it would last a long time.

At least, the developer should specify how long the product will be supported for security and bug fixes.

A great solution, if you can pull it off: You continue maintaining the base product indefinitely, but "v2" features are disabled until the user pays more. And if you buy v2 in full you get the full feature set.

I don't really care about any of that. I just hate when a product is advertised as "one time purchase" when it actually isn't. I haven't got a single problem with developers charging for a new version, just be crystal clear about it.