I did a few of these in my early days. I don't remember any actually taking three hours and my average was around an hour and a half. The data entry was only about five minutes because then only incorrect prices had to be entered. Other than one crappy store, I never had more than two or three incorrect.
To me the biggest issue is the employee. It is impossible to complete the audit without one and would probably take even longer. So you end up in a situation where the employee will determine how long it takes. I was lucky enough to have some great managers to help me knock them out quickly. Only once, and it was the store with a lot of errors, did the manager slow me down. Every time we found an error she was taking the time to correct it on the spot. She also had some of the worst employees imaginable so we kept getting interrupted. That audit still only took two hours.
Equal rights for others does not mean fewer rights for you. It's not pie.
"I prefer someone who burns the flag and then wraps themselves up in the Constitution over someone who burns the Constitution and then wraps themselves up in the flag." -Molly Ivins
Never try to teach a pig to sing. It's a waste of your time and it really annoys the pig.