In my consulting and training practice whenever I get to talk to project managers, both experienced and new, the question of whether it pays off to be honest when interacting with your clients always comes up. I usually say that it is much easier to weather the storm at the beginning of the project than to suffer the death of the thousand cuts through the entire duration of the venture.
However, one time an experienced project manager approached me after the session and, with a "wink wink, nudge nudge" look on his face, said the following:
"Oh, c'mon, man like you never lied to your customer in order to get the project off the ground! You know perfectly well, once they get a little bit pregnant, there is no way back for them!"
Once I got over the painful image of "getting my customers slightly pregnant", I remembered the following dialogue I had with my former boss, the director of the IT department at a global bank.
Director: Hey, I am going to assign you to this new regulatory project. Keep in mind, this is a high-profile endeavour; our main client is the Senior VP of our company. By the way, you should not, he is a very difficult individual. As a matter of fact his nickname in our department is "El Diablo"!
PM: Yes, I have heard about this project. I have spoken to some of our technical people and they have estimated the project to take about nine months ...
Director: Yup, that is another problem. I have personally promised that we would deliver the product in three months
PM: “What?! Three months? But now that he finds out the truth he will be mad!”
Director: “Don’t worry about that. I have a plan. We will proceed by breaking the news to him gradually!”