I drove to OHare from Tinley Park last Thursday. I left Tinley at about 2:15, and was at the ORD exit of the 294 by 3:15 or so. It then took me about 30 minutes more to go the last 2 miles from the exit to the rental car drop off.

Also note that those last tolls are not manned, and only accept coins. If you have no coins, then you have no recourse but to drive through without paying. There's a sign on the side of the collection box that says you can pay online, but it doesn't give the web address. Not very visitor-friendly, I must say. (Pretty much in-line with my entire ORD experience).