"I really wonder how many PPL's follow the military rule of thumb of roughly 3 hours prep for 1 hour's flying"
Oh come on! What an incredible waste of time 2.5 of those 3 hours would be.
On that basis how do you explain a low level military Jetstream very nearly T-boning me at 500ft while in the circuit at Bodmin and well within Bodmin's ATZ back in 2002? Maybe the Jetstream crew on that day needed more than 3 hours prep? Or maybe they're just human like the rest of us and balls it up occasionally too despite all the planning. Answers on a postcard please...
Weather prep is far more significant to light plank operators with or without the IR.
Nav prep is a moveable feast and can be done preflight far more rapidly nowadays with navigational software and (relevant) NOTAM downloads - how many times have you been able to maintain the chinagraphed line on the chart for a 100 miles leg at 2000ft? Didn't think so, me neither (the only time I have managed to go in a straight line or on a pre-ordained course for a heck of a long way is in an airway above the weather and in class A airspace). Some element of re-planning in the cockpit is an essential in-flight activity on almost every VFR low level flight I do. This is usually due to weather if there are cells of CB around.
SB