Source: Speed matters: Why working quickly is more important than it seems, by James Somers
The obvious benefit to working quickly is that you’ll finish more stuff per unit time. But there’s more to it than that. If you work quickly, the cost of doing something new will seem lower in your mind. So you’ll be inclined to do more.
The general rule seems to be: systems which eat items quickly are fed more items. Slow systems starve.