1. Keeping a good notebook means not having to repeat work because you can't remember what you did. Being unable to reproduce my own work was a massive handicap.
2. Your results "decay" over time. Even if nobody is counting your hours, the level of intensity required to overcome that rate of decay is intrinsic to the nature of the research itself.
A potentially useful clarification on what good means: on the one hand it should be easy for you to write to it, on the other hand it should be possible for you to search through it. I find myself re-deriving the same gradient over and over...
1. Keeping a good notebook means not having to repeat work because you can't remember what you did. Being unable to reproduce my own work was a massive handicap.
2. Your results "decay" over time. Even if nobody is counting your hours, the level of intensity required to overcome that rate of decay is intrinsic to the nature of the research itself.