It has been asked for countless times before, but I can't find it on Canny yet. Add a PARCEL_DETAILS_AUTORETURN_TIME to llGetParcelDetails or make a new llGetParcelAutoreturn function.
Yes, there is a potential griefing angle here, but whenever has that not been the case? This feature has been asked for so long and so consistently and would make life so much easier for legitimate scripting tasks.