Not that different than the established charter operators who for years have flown more aircaft in the higher revenue months than in the winter. There is no public service obligation on any route.
Not so long ago Ryanair were running out of flying hours and had to curtail some winter schedules as a result. Now work the guys to the limits in the summer when you can earn more and less in the winter with a change in destinations reflecting change in demand ii.e skiing and canary islands.