It rather depends on the type and the airline concerned, in my experience.
Considering the same type, at one airline the brake cooling requirements are advisory only, whereas at another they might be considered as mandatory.
This is because the specific type, altho having brake temperature gauges fitted originally, had them removed (for a variety of reasons) and this was permitted as they were listed in the MEL as not a required item.
Having said this, crew that treat brake temperatures as advisory only, may well find themselves in the poo if a high speed reject is required and the aircraft ends up in the weeds...the respective fleet manager will certainly not be pleased.