The cash bids update from 9:30 a.m. until 1:45 p.m.  The updates may be delayed up to 20 minutes.  The cash bids do not change from 1:45 p.m. until the CBOT daytime markets begin again at 9:30 a.m. the next day.  If you roll your mouse pointer over the little clock symbol next to the cash price, it will tell you when the bids were last updated.