Since this is in the fractional forum, I assume the schedules we're discussing are for fractional flying.
There is no way I would want to work longer than the 8 days I currently work - in the fractional environment. Packing for longer than that is an issue. Most tours over the last year have been so busy there wasn't time to do laundry. When you're being scheduled for 14hr duty days (not to mention the 10 in 24 flight hour issues) back to back to back, your duty "free" time leaves you little time for more than a quick bite, maybe some exercise, and, hopefully, restful sleep. Of course several of those nights are going to result in something less than restful sleep, so cumulative fatigue becomes a factor.
If a 15 on 13 off schedule has some guaranteed extended rest days, or if the type of flying leaves you on reserve at the hotel for a few of those 15 days, maybe. But trying to work that schedule in our type of flying is, in my opinion, dangerous. If they tried to implement that system-wide, the fatigue calls would come fast and furious starting at about day 7.
Of course our schedule can't be modified without amending our union negotiated contract, so 15-on, 13-off ain't happenin'. And I'm protected from retaliatory action should I call fatigue. Not all of the fractional companies have those protections. But thankfully, we do.