Like what Ryan says. I hadn't really put much thought into it until probably about three days ago. I was pulling into the garage and went to apply the brakes as I normally do, but the pedal travel greatly increased and I ended up bumping my sons ATV bumper. I asked my wife about it as she runs loads for me a lot, and she hadn't recalled any such incident. I would say it has happened to me, maybe 4 times in all my miles. I don't ever do real heavy braking and use the engine brake in correlation. So nothing was over heated. And I hauled about a 1/2 load in it last night and had no issue. I checked the fluid and it looks fine. I also had all the tires off last week and upon visual inspection, nothing was wrong with the discs in the front.
I know someone here mentioned the parking brake. I do use it, but again, can't verify it's use before each incident.
I am keeping a lot closer eye on it now to see if I can narrow down an issue of cause.