It is very simple. Even if you are a responsible driver who doesn't think public roads are a race track, you can be driving the wrong vehicle for your intended use and need that last few % braking performance.
It will usually be the pads that can't handle it, or overall brake system wear not the fluid age, but replacing fluid excessively ( more often than once every 6 years or so) is a band-aid hope to eek out a small % improvement in a brake system that is inadequate for the use.
It is the cheapskates who think they need that frequent, fresh brake fluid change instead of upgrading their braking system, "IF" anything was needed at all instead of them just believing urban myths that following some set procedure was a placebo for braking problems.
If you don't have braking problems, you don't have braking problems. It doesn't get simpler than that. You don't need newer fluid if you don't have braking problems caused by old fluid. I know, it's rocket surgery.
Then there's the chicken littles who say what if the sky is falling and there's some sudden life or death event. NO. Your brake fluid does not heat up enough to boil fluid from a little moisture in it, from a rare, sudden even. It does that if you are driving at the limits of the braking system because you have a setup not suited to your use.
On the other hand, it is true that brake fluid is cheap and some of you need a better hobby but this is what you have so you change the fluid whether it needs it or not. There are worse vices in this world than that, but many of them give more satisfaction than the thought that your inadequate brakes now have fresh fluid.
Decent brakes don't stop working from some water vapor in them. Once ABS came along, brakes could be set up with much more stopping power because it wasn't solely dependent on the driver to modulate them. Your use scenario may vary. There are always exceptions, but the general urban myth about always using new fluid and changing it every couple years, has no basis in fact/science except in the most extreme conditions, that whole last few percent crowd who doesn't have any common sense and only understands if one number is slightly higher/lower than another number.
Everyone raise their hands if their primary criteria buying a vehicle was its stopping distance while racing. It IS BITOG, there are bound to be some people out there who legitimately have this need. Everyone else, should observe the millions of real world examples of brakes working fine all day, every day, with old fluid.
Toothbrushes are cheap too, and every day you use a used one, you risk infection. Do you buy a new toothbrush every week, let alone every use? Do you submerge it in sanitizer instead? I don't, 'cuz I'm
living on the edge.
Believe it or not, OEMs actually test things like this and don't just forget to tell you to change your brake fluid. That is a very important system in a vehicle and there would be massive recalls if it didn't work safely by following their service intervals. If your vehicle OEM states you need XYZ for your brake maintenance, do that. Rest assured that they have tested this and have far more data than some internet jockey.
