+1. Outside hourly contractors, if you have a clear sense of what impact/outcome you're seeking, time of day or number of hours shouldn't matter. Often I suspect it's a proxy for NOT having a clear idea of the desired outcomes. Removing a requirement for "8 hours a day" can even be a good forcing function to ensure you DO have a clear and well-communicated set of goals and outcomes. Indexing on time (IMHO) can also have unwanted side effects like people just filling in the time "because they have to", which is pointless for everyone involved.