I'm sure these chaps are only choosing to do this in situations that they are very familiar with i.e. without an up slope, no airbridge, maybe self stopping, cute FO that needs to be impressed etc... However I really would like to know if this is something that has been suggested within the airline to save fuel and time. Further to this, the same low cost airline only uses 1 minute cool down time for its engines rather than the Boeing time of 3 mins - sad I know but I've timed it!