Sorry but your post is ridiculous.
Lets assume that the average gamer who works and has a family only manages 2hrs of gaming a day. That means to complete a 24hr endurance they would have to leave there PS3 console on for 12days!
Besides this you know very well that a majority would probably spend between 2-4hrs between saving and not 15mins.
I agree with you, endurance save option would be great, but if PD can doing, they will, but if not, then us family/working (two jobs) guys are screwed (damn I wish I never got married and started a family or started to work and play in a bend, GT5 is the only purposes of my existence) and without a save option, i will never finish GT5, and i will not be truly fulfilled.