Best advice I can give you is to thouroughly clean and degrease the engine and underside of the car. You'll need it to be clean so you can try to determine the origin of the leak - very likely valve cover seals but could be at any joint.
Why a bigger puddle after a long drive? Well, if it leaked at its normal rate, but for a longer period of time the oil could very well pool somewhere, and then drip for a longer period when you stop, leaving the large spot on the driveway.
Use several peices of news paper or sheet of cardboard under the car to try and help locate exactly where the oil is dripping from. Sometimes helps to know this when trying to backtrack the oil.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.