Personally I'm a big believer in having plenty of hours. While some low hours people are extremely capable, and some high time people are awful (both as pilots and instructors), in general I feel that hours gives the instructor:
1. Confidence in operating the aircraft in a variety of locations/weather conditions as well as being better placed when the aircraft malfunctions
2. Direct experience of dealing with various personality types/learning styles (ideally this would allow the instructor to create a learning environment which suits each student...not always the case, I accept!)
3. Credibility.
Although there is no set minimum, even the lowest-houred CFS students will have very nearly 1000 hours before they start the QHI course. How practical is this for the civ world? Not at all, I'm sure!