Another company using this model very effectively is Derivative, makers of Touchdesigner. Licenses are sold at an initial price that includes a year of updates

Another company using this model very effectively is Derivative, makers of Touchdesigner. Licenses are sold at an initial price that includes a year of updates. Once that year expires, the newest version (old versions are kept available on the site) within your update period will continue to be usable with your license - which is freely transferable between machines. They offer a couple license tiers, custom work, and paid support hours. They even provide a free non-commercial license that is minimally limited and great for learning. The other great thing is that they are highly responsive to user feedback and bug reports. I've had a situation before where we found a bug in the course of a project and they fixed it in a matter of days, had a build sent over in time for my deadline, and then the fix was pushed for everyone in the following update. I frequently point them out as a model for the best way to offer a software product to both a professional and amateur market. It's essentially all the benefits of perpetual licensing while still providing a revenue stream for the company and ongoing support for professional users. No direct affiliation, but I've shared drinks with the devs and am a very pleased user.