Why has the love affair between BEN AFFLECK and MATT DAMON lasted so long?  It's a question of trust.

Ben says, quote, "The nice thing about working with Matt, somebody that you've known a long time, is you don't have to worry about how you're going to get along or what the process is going to be like.

"We've developed a pretty good story over the years and we don't lie to each other.  If it's not good, we say it's not good.  And it makes the whole process a lot easier."