Many interesting comments of fuel planning.  Here's a few "comments on the comments:"

Some said that more fuel equals more safety so they always fill to the top.  Okay, but I didn't hear them say they would also top the tanks before the trip home - I suspect they wouldn't do that for the 30-minute flight (I wouldn't).  So how can safety be improved by NOT filling the tanks?  For me the most worrisome part of the flight is the climb to altitude - the sooner I can get there the better.  Unnecessary fuel reduces the climb rate and increases the time exposed to the risk of engine failure.  Are there other safety advantages to having LESS fuel?  Might be, but that's the one I can think of.

I certainly agree that one doesn't ever want to take off with the fuel quantity on board being "unknown" and there were a number of posts that discussed ways to reduce the uncertainty.  I would think, however, one could dipstick the tanks before every flight to make the fuel a "known" quantity.  I dipstick the tanks and then check the fuel gage readings against that known quantity and then sort of triangulate the fuel with the initial known quantity, known fuel burn rate and the fuel gage readings.  If at any time the fuel gage readings are less than I would expect it is time for a landing to find out why(fuel leak?).  If they are more than I expect I certainly don't extend the flight, assuming there is more fuel than I planned(bad gage?).  Everything should match the prediction and the only way to do that is to dipstick the tanks.

Reminds me a little bit of the pilot who told me that he changed oil every 25 hours because oil was "cheap insurance."  Okay, if it actually did improve the reliability or longevity of the engine, but there is no proof of that.  And all those oil changes increases the chance that something will be done wrong.  Does more fuel always equate to more safety?  If so, maybe it is "cheap insurance."  Problem is, I've heard the term "cheap insurance" used badly too many times, so it makes me nervous when someone says that.

Oh, yeah, and if you are going to make an off airport landing the safest way to do that is with empty tanks......:-)

The only absolute is that there are no absolutes.  There are no "safe" airplanes and no "dangerous" airplanes as well as no "safe" flights - we can only operate somewhere in the range between safe (don't go at all) and dangerous (don't do anything really stupid).

Gary