Different guns in combination with different ammunition require differently cleaning schedules.
Over time, you will get a fill for it and know exactly what your gun requires.
In general, the firing pin channel shouldn't get too dirty, if you leave it dry or very slightly oiled.
In that case, clean it every 2000 rounds should be sufficient.
If you do oil the firing pin a bit too much, expect the grime that find its way inside the channel to stay in there.
In that case, perhaps every 500/700 rounds.