Ever replace the front calipers and brake hoses? A sticking caliper or collapsed brake hoses will make the pads have too much drag on the rotors. The further you drive the hotter they get. Bet that why it seems to do it after driving some. I would replace the front calipers and hoses.

What a voice!!!!

http://www.godvine.com/10-Year-Old-Boy-with-Autism-Sings-Open-the-Eyes-of-My-Heart-1041.html