The wind is your friend....or your enemy. Usually, the jet stream will help you going east and hurt your going west. I did a x-country from Meridian to SD and back....going out I was fighting a 70 knot head wind and was only getting about 400 mile legs. Coming back I got to 41,000 and a 100 knot tailwind....did a 650 mile leg from Yuma to Lubbock with enough fuel for 2 approaches....then from there to Meridian at 670 miles..with fuel to spare. Needless to say always, always check winds at altitude before you strap in and always plan a divert short of your intended destination.