Not sure if you've got the same issue but here goes...
I noticed that my brake pedal was getting "spongy" and would require me to stand on the brakes (almost literally or so it seemed) in order to stop the LC. I kept thinking something was wrong and took it to dealer #1 who claimed everything was within normal tolerances. Honestly? I'm not sure they did anything with it except drive it to lunch. I drove it for another couple of weeks and continued to complain. Then for some reason, my wife dorve it and told me she was afraid she wasn't going to stop. Still no proof...then I rear-ended a guy because the brakes wouldn't stop the car. I took the LC to dealer #2 and explained to them what was going on and that it felt like the old days when a master cylinder would malfunction but it wasn't doing it all the time. They drove it in the morning and didn't notice anything...drove it again in the afternoon and sure enough, the problem surfaced. They diagnosed the problem as one of the internal o-rings inside the master cylinder. It wasn't allowing the pressure to work as supposed to. See? I told 'em. Anyways, a quick part order and back to no spongy brakes that actually stop.
If this sounds completely different from what you're experiencing...well, I'll hope that this is an anomoly.