Head injuries are really serious. There is no race or event or whatever that is worth rushing for when you have a head injury. There's always next year, 5 years from now, next decade.
As far as road rash goes, I've slid on the pavement at about 30 mph on a Tuesday night. By the next Sunday I'd removed all dressings. Monday I raced with no road rash (although I had pretty fragile skin in spots). So, properly taken care of (I followed my own recommendations posted earlier in this thread), it's possible to get rid of most superficial road rash in less than a week.