We often preach about how important it is to have enough fuel to get to your destination — odd that running out of gas should stubbornly continue to be a cause of accidents — but there's a flip side to having enough fuel to get where you're going: having too much fuel too soon.
For years I used to top off the airplane when I got back from a trip, expecting that I'd just be hopping back in the cockpit again all by myself for my next journey. Then one time an unexpected family trip came up, along with the all the bags and kids and more bags and sure enough, I had too much fuel.
De-fueling is no fun and it takes time. Had I instead waited until the day before my next flight, I could have very easily have asked the line guys to fill it to the tabs, and everybody would have been much happier. (I wonder how many flights have staggered out over gross weight under these same conditions.)
The other consideration is time of day. If you fuel when it's cool but wait to fly until it's hot, you'll be losing fuel as it expands and exits the fuel vents. That's another time it would have been wise to wait.
Of course, you need to be smart, too. Don't wait if there's any question about whether you'll be able to get service before your flight — my FBO at Austin Executive (Henrikson Jet Center) is open 24/7, so all I have to do is give them a call an hour before I launch and I’m golden. But if you're not sure how much fuel you'll need, by all means be patient.
Not having enough fuel is the bigger issue, for sure, but you also don't want to have too much or, sometimes, the right amount but too soon.
