Why is the usage period of digital editions from Ernst Klett Sprachen limited to 1 year for students and 3 years for teachers?

This is very similar for all publishers. Rarely does a course actually last longer than 1 year; if it does, we extend this licence on request and in goodwill.

The reason for this is the warranty: we have to keep each content on several platforms (Apple, Android, etc.); unfortunately, we cannot grant longer periods of use here; the comparison with a print textbook can thus not be made.