yeah, leg length or total length of flight is irrelevant. It is all based on DISTANCE from the DEPARTURE point. Draw a 50NM ring around the departure airport, then fly outside that ring.
For an ATP, you are done. The flight counts regardless of where you go or what you do after that.
For PPL, CPL, IR you need to land somewhere before you fly back into the ring. Touch-and-go's are a grey area here, best to do a at least a stop-and-go.
Once you leave the ring, you do not need to go back inside...ie you could land and spend the night (or weekend, or whatever).
Also be aware that the FAA may not want you to do a 51NM XC flight, do airwork for two hours, and then log the whole flight as XC. It's not defined by the regs that you have to be "enroute" the whole time, but use your judgment here. A few practice stalls or slow flight enroute would be OK but probably not extended airwork in a practice area.
Last edited by rickair7777; 10-14-2009 at 08:41 AM.