The business of FR grounding it's fleet over winter is being made out to be the only sensible and viable way to run an airline.
Not necessarily. He gets away with it because most of his workers are contractors who don't get paid unless they are flying. He also screws his suppliers down so that there is no fixed costs element of their contracts.
Other airlines mitigate the winter months by wet leasing. Others make stonking profits in the summer to offset lower cashflows during winter.
Most businesses have a seasonal aspect to them. Aviation is no different.
FR was lucky enough to have gotten its aircraft at heavily discounted rates. Therefore having the aircraft parked up is not so much of an issue for him, whereas it would be for a national full service airline. He will never get these discounted rates again from Boeing or Airbus. His maintenance costs are starting to rise with his fleet age and he is having to face the reality that he will start incurring significant and unavoidable costs unless he ponies up and buys some new airframes at the going rates.