I don't necessarily agree there. My car runs at about $0.13/mile for gas. If I go 3 miles each way out of my way that's the equivalent of $0.08/gallon extra for a 10 gallon fill-up. Maybe its worth it, maybe its not. It is rare for there to be more than a couple hour lag between when the first station raises its prices and the last does around here. I used to have an independent station near me that was about a day late, but they went out of business (probably because everyone dashed there and sat in line when the gas price went up).
As for the fuel temperature, it always seems about the same in the tank. I have to be careful in the summer when I fill gas cans because the gas expands about 0.1%/°C, or about a pint on a six gallon can for a 36°F rise (55 to 91). If I fill the can to the top with cold gas, it will overflow once it warms.
I placed a red plasic gasoline can in the sun with a pressure gauge connected to the vent port to demonstrate to my son why he should leave the vent cap open when he put a can in his pickup bed; after 45 minutes, the can was up to 5PSI and climbing.
I only put two gallons in my 21/2 gallon can and keep it in the shade.