Well, as a manager I can tell you that it is company policy in every company that I have ever dealt with that lying is a dismissable offence. The official term for it is 'a breakdown in the trust relationship between employer and employee'. If they find out you will definately be very much on the back foot, and that may come back to haunt you in the future.

Think about it, your boss knows you lied 3 years ago to get the job, and comes to you and says he wants you to work every weekend for a month. Can you really afford to say no given that he could have you dismissed for lying to get the job in the first place. I know of so many people that have lost their jobs for less.

I'm not suggesting that you dismiss the suggestion, just be very, very careful if you decide to do that.