Any Time, All The Time

I had lunch today with Mr. Westfield, Curt Whitesell with WKRP Indy, and he said something I have heard a couple of times lately.  He said, "Rates change once a day, right?"
Au contraire mon fraire.  Mortgage Interest rates change with the market and are subject to change at any time, just like the price of a stock. 
Since early May the market has gone up and down like a Yo-Yo, and so have interest rates.  It has not been uncommon for rates to change 3-4 times a day.  So, when your Mortgage Professional says, "Lock now!" you should jump before the market changes.