In terms of Valve Time, I've been struck by something John Carmack said[1]:

"that was id’s mantra for so long: 'It’ll be done when it’s done.' And I recant from that. I no longer think that is the appropriate way to build games. I mean, time matters, and as years go by—if it’s done when it’s done and you’re talking a month or two, fine. But if it’s a year or two, you need to be making a different game."

1) http://www.gamefront.com/john-carmack-on-doom-4-id-quake-liv...