I heard of this story, and it showed the strength of conviction needed to send a message: discretion extension is at the behest of the captain/crew NOT the company. Sensible rostering is very necessary, both for efficiency of schedule and human factors.
5th day, running up to max accumulated duty, and a long out/back night flight on the last night. Crew was tired due lack of sleep in hotel during the afternoon. Nigh impossible. Accumulated sleep deprivation was having effect. The departure was delayed sufficiently that there would not be enough time to complete the return sector without full discretion. Captain told OP's at departure that they would not complete the return but night stop to rest. Please organise hotac and inform the agent and pax well in advance. A/c arrived at destination and agent started boarding. Captain was very displeased etc. etc. and told the agent to inform the company they would operate the return until out of FTL and land en-route to take minimum rest. He nominated the landing airfield, which was a company route destination, so the company could position a SBY crew ASAP. He landed to find no crew had been arranged. The company called the crew's bluff and lost. He'd told them twice; and this was after discussing the 5 day roster as being unreasonable BEFORE he'd started it. Just how deaf can some people be? Being a union airline helped too. Hate to think how guys survive when on their own and hanging in the wind.