If you're braking a lot (on long descents, etc) then the rims can get very hot. Carbon rims are not as good at dissipating the heat as metal ones and that can lead to problems with the rim. Metal rims also have problems with heat, but you wont damage the rim itself. In extreme cases the inner tube can explode or tubular tyres can slip off when the glue becomes softer in the heat.
Disc brakes get hotter than rim brakes, but they dont have the problems where it can cause a sudden tyre/tube failure.
No, but you can boil the fluid and leave yourself with no brakes.
Three words...Gore Bike Wear.
went into a bike shop today, and I almost bought a Gore jacket, but I didnt in the end, i bought an Altura Night Vision as i didnt want a jacket for extreme cold
The Altura is like a long sleeve jersey with propoties of a jacket, windproof, lined and is water replent in some areas, will be wearing it tommorow, oh I did try on quite a few jackets, but this one DID fit me!

I then turn off but I don't have time to turn round get an idea what's going on and how he can be so quick on that type of bike.
Is there something I'm missing?