Brevity without loosing clarity!
Brevity without loosing clarity is, IMHO and experience, most effective!
Also depends on:
First flight of the day/week/month/year for this crew pairing?
Airline crew - (same routes) or full-time vs. freelance corporate/GA or non-scheduled environment.
I agree with previous posts that it should include a (brief) discussion of Chart(s), Terrain, Weather and Operational considerations/threats concluded by the safety (emergency) bits!