The App Store policy and the longstanding Omni Group policy agree: minor updates should be free. If there is a major overhaul of the application with lots of shiny new features, we may release it as a new product, and that would cost money. Bug fixes, minor features, and miscellaneous polishing come at no cost.
On average, we offer free updates (new releases where we fix bugs, and sometimes add new features) every few weeks or months. Upgrades on the other hand (where we add major new features requiring a great deal of development) generally happen on the scale of a few years.
When we release major new versions, we offer upgrade options through our Omni Store, and we do our best to offer comparable options when we can through Apple’s Mac App Store and iTunes App Store.