EDDF RNAV arrivals contain many track miles to touchdown with heights and/or speeds at some designated waypoints. It's unusual to fly the entire arrival as published but you don't know which waypoint you maybe short tracked to by ATC. It's mainly dependant on traffic and you cannot always assess it accurately yourself as TFC will be entering the arrival procedure from different sectors and therefore from different frequencies however TCAS does help. The secret here is to program the FMC to be as low as possible and keep the speed back to the minimum the procedure allows modified by your assessment of the traffic. Some of the controllers will assist by telling you expected track miles to run and or to plan to be a particular point at a height &/or speed though not yet cleared to do so. The incidence of observing a/c being high appears to have dramatically increased since the introduction of RNAV arrivals at EDDF. This is not to say the design is not the best but that Pilots need a better understanding of the reason for the design, how the arrival process is used for max efficiency and how to operate their a/c in accordance to it.