It's a tough one, if you did keep to this scheme I think you would miss a lot of stuff that helps you with the productive goals you are trying to achieve. It's not really something you can plan out either, a lot of the really valuable stuff and new ideas that help me both with the programming and business side of my startup I just stumble upon.

Limiting yourself would get more work done but there is always the danger on putting your head down and plowing on in one direction only later to realize much better ideas or methods that you didn't know about in a more closed loop.

Of course there is a load of middle ground and I guess that's what most of us here try and work towards.