Practically I don't do it, cognizant it may not be a rational choice but rather an emotional one (or possibly it is long term rational - I don't want to support that model for apps that don't need updates, further development, or online / server support. E.g. Why is a file duplicate detection app, or file sync app, or data recovery app a monthly fee? If you made it well once I don't need to update it virtually ever - or if I do, than the features must be massive and it's ok to have ver 2 for money. I feel subscription is often a money grab, life fitness hope that people will forget to cancel, rather than some mutual value proposition.)