I rarely hear flight plans mentioned on the R/T. On landing it is the tower assistant who sends an arrival signal via the AFTN to the departure airfield, but this is never mentioned. It is assumed that it is done. A pilot is only required to request the closure of a flight plan if he lands at an alternate which was not declared on the original plan (and ATC fail to ask). If due to headwinds a pilot finds that his ETA is going to be half an hour or more later than his declared estimate, a revised E.T.A. needs to be passed. But this really only applies to flying in the FIR, not on airways or other recognised routes because the ATC computers work out your actual groundspeed and thus your E.T.A's which is why they are not passed (in Europe or the U.S. anyway).