For myself I purchase only non-expiring licenses with a one-time fee. It is absolutely fine if I have to pay again for upgrades from time to time, but I want to be able to decide to not upgrade and still use my work for another 20 years, when the vendor is already forgotten. And provided, I still have compatible hardware ;-)

A good example would be Softmaker, which I am happily paying for (but they also nag me every other day, if I wouldn't rather like to switch to subscription).