Haynes Manual Oil Filter Change Schedule

I've had my Discovery 2, TD5, now for about seven months. I changed all the oils when I bought it. For the engine oil I replaced both filter cartridge and centrifuge at the same time. It's now done just over 4K miles and I am planning to change the engine oil again.
While the Haynes manual recommends that the oil is changes at 6 months/6K miles, it interestingly says that the oil filter cartridge need only be changed at 3 years/36K, and the centrifuge at 24K/2 years.
Is this correct? I am only an amateur with cars but I have never not changed the oil filter at the same time as an oil change. I can't find anything on previous threads about this either.
I know that these filters are not expensive, but can someone tell me please whether it is not necessary to change the cartridge and centrifuge every engine oil change!?
Thanks

Better keep up with the good practice and change the whole lot every time. BTW in RAVE's maintainance sheet the rotor filter must be changed at every oil change

Thanks. I agree. I find it odd and interesting that the Haynes manual says three years/36K for the oil filter.

That's what RAVE says too for the filter and IMO is b0ll0x

Seeing as you are not charging yourself for labour, change the lot every time!
Do grease or Copaslip the threads of the centrifugal filter bolts the first time you take em out as they have a tendency to strip the threads of the part they bolt into!

I get the OEM filter set from Island or similar (DA6004P, iirc) and change everything, including the fuel filter. Doesn't take long and as I do it every 6k miles, nothing gets too stuck either, although the fuel filter can be a bit 'will it or won't it'. Don't forget to make sure all the old 'O' rings have come out too.

Myself I do oil every 6000 with oil and filters on every second change. Having two filters does make a difference as the oil takes ages to change colour, other diesels iv had oil goes black rapidly.