I have a thorough brake system flush and fill done every brake change (about 3 years or so).
When I do it, I upgrade to DOT5.1 Motul, or Stop-Tech STR-600.
I have a brake bleeder vacuum system used and crack all four bleeders at the same time. From start to finish I go through about 2-liters of fluid to get a thorough flush and fill.
I do a front/rear/parking brake service every year in the late spring to ensure everything is moving well and the wear is even.
I do use my parking brake a lot so it always works, especially when on hills pointing up or down as it takes all the pressure off my transmission pawl.
Then I get my truck Krown sprayed and have them also coat the calipers and hubs, too.
My brakes have never failed me; I can stop on a dime & make change... lol