Doesn't matter if you use your cruise control or not, the circuit in question has power at *all* times, even when the truck is off.
The question should naturally arise as to how brake fluid is allowed to leak onto the wiring harness; many fast lube joints top off master cylinders when replenshing fluids while a competent mechanic never advises doing so unless the fluid level warning light is on, and, even then, such a condition warrants a fluid system integrity test.