About once a year before, but in the last 3 months 4 times.
Where you fly and how good ATC is makes a big difference. Obviously West-Africa lacks something in the ATC department. Most of their airports have single RWY only and no taxiways. There are plenty of Russians flying around with heavy crew ( Capt, F/O, F/E and Nav ) and with lots of misunderstandings about clearances.