I've been working in IT and software development for 10+ years of my life. In all those years I have been rarely thanked for my time if I didn't know the answer to the problem. If an end user spends 2 hours on the phone with you only for you to give them some form of "I don't know" then they will see you as nothing more than 2 hours of wasted time.
It's also not fair for the little rookie who made the last three point shot that put the team 1 point ahead in the game just as the buzzer sounded to be hailed as a hero with no consideration to his fellow teammates that had been fighting the good fight and holding the line since the beginning of the game.
But that's just the order of things.
JamesNT