How often should we change fuel filter?

[notorious]

Cheers Neil. Just ordered.

Here is the kit you need if you want to do it yourself for the following engines:

V8: AQG,AQF,ARU,AQH,AKC,AVP,AUW,AVN,BCS,AYS
V6: APR,AQD,AMX
W12: AZC

Fuel filter: 441 201 511 C
Two filter crush washers: N 013 81 28
Two more filter crush washers: N 013 81 49

Torque 23 Nm.

Optional hardware (in case you never changed it may be rusty and worth renewal):
Bolt: N 906 264 01
One more bolt: N 021 07 47
Screw: N 904 968 02

You will need to remove plastic cover to get access. Another 6 rusty bolts (optional):
6 bolts: N 090 11 62