It's not just us. From the Delta section:
FDP extension email from mgmt
Haven't had to extend yet, but have pre warned them that by the time a replacement airplane came in and we could make it back from the outstation we would not be in any condition to continue to our scheduled overnight. Got to go home for the night while my commuting FO did get a hotel paid for in domicile, and we all continued the trip the next day .
It's an easy no brainer for me. Fatigued it is, with an easy justification that I was prepared and rested for the scheduled day, but was unable to continue past 14 hours. or whatever the convoluted 117 duty time was.