Well, a run up is important first thing in the day. After you've already flown once, I normally just do very brief mag checks and prop checks on my taxi out for the next flight. On long cross country flights, I periodically check the mags in flight when I can remember to do so. Only time I redo the full run up if I've already flwon is if I've shut down and parked the aircraft and had it out of sight for a couple of hours and/or the engines have cooled down considerably.
Last edited by AdamFrisch; 16th November 2012 at 23:41.