Never.
You may have to talk with the service mgr if their messing with your tire pressure.
Tires on a trailer need max pressures. Now if someone has over tired the trailer (E in place of a C) then you may need to use less pressure.
rvsafety.com
Tire Load and Inflation Ratings
Note: Towable – Travel Trailer/ 5th Wheel owners Due to the severe use conditions experienced by tires when axles are very close together – tire industry experts recommend maximum (sidewall) inflation pressure for towable tires unless this causes a sever over-inflation situation (20psi+), often referred to as the ‘basketball effect’. If this is your situation allow a 10 – 15psi safety margin above the minimum required inflation pressure."<<<<<<<<
Also a D or E tire at only 50 psi can run much hotter than the same tire at max pressures. If you checked them immediately after getting home they may have gained some pressure.
I've seen my E tires (cold set to 80 psi) go to 92-94 psi after a hard run on a hot day.