I wear similar oakleys. 4hour in 40 degree heat isn't a big deal...the ones I own, have vents and baggy enough to allow air in. I have done 6 hour rides in them.
Is it necessary to be so insulting? I wear gear like that and ride up, down and all round. I can make the assumtion your bike control skills stink and you wouldn't know what a REAL dh section looks like due to your last statement, but I won't.