I recall a quote from my Flight Time Limitations agreement with a former employer which stated: "For the avoidance of fatigue, rest periods of 18 to 30 hours should be avoided."
CTF
Under CAP371 this was aimed at UK flights operating to Florida under day/night rotations. It could be argued that it was also for switching from late's to early's to nights but that was because of CAP371 regs that no more than 3 could be operated. Thank god this rule will go under EASA and some common sense can be applied to roster patterns (and for avoidance of doubt backed up by science by UK AOC's who have approved FRMS so plenty of science work on consecutive earlies lates and nights)
18-30hr rest periods have also been challenged on night / day rotations as this pattern allows crewmembers to start the recovery in company time compared to at home.
Finally my only other advice to others reading the post would be trying to argue the point with Crew Schedulers is a waste of time. If I have a problem i'd go to the Chief Pilot my boss.