I'm a big fan of the way JetBrains sells their licenses. Like a lot of software companies nowadays, they only sell licenses on a subscription basis. But with a very customer-friendly clause of where if you pay for a subscription for 12 months you get a perpetual license for the latest version of the product when you initially subscribed. And then after paying for any particular version of a product for 12 months, you also get a perpetual license for that particular version and so on and so forth.
Their FAQ page explains it a lot better than I can: https://sales.jetbrains.com/hc/en-gb/articles/207240845-What...