With Sketch, the 'cons' are that if you withhold from upgrading, then after some time the app will get increasingly less useful: plugins are generally supported

With Sketch, the 'cons' are that if you withhold from upgrading, then after some time the app will get increasingly less useful: plugins are generally supported only for the latest version, and it is rare when you can get old versions of plugins. Design resources too always seem to be available for the latest versions only. So if you work completely independently from external world, it migth not affect you much, but if you are not, it is cheaper to buy upgrades. Maybe not every 12 months, but every 18 months or so. But anyway Sketch is that good that we pay it's price gladly.