rc.local gets called from rc.S....
rc.S is the place for it!!!!! Hell, you could put it in rc.alsa, and it'll still work.
It does take awhile on bootup tho if you have lots of stuff in there and your using an old computer. That's why I echo "cleaning /tmp" so your not sitting there wondering what's going on.
Would you rather wait to bootup or wait to shutdown/reboot. Either way your waiting...