They definitely can change. Last time we went the hours were topsy turvy, but that was because they were getting ready for the 60th.
If the crowds are busier than expected they can open earlier and/or close later. Typically busy days (weekends, holidays, summer) DL opens at 8AM, semi-busy days they open at 9AM, and the off season hours are 10AM. Likewise days that open earlier usually stay open later. You can always check back the day before, and it's possible even the day of if it's significantly busier than expected they could change the hours and stay open later.