I'd just change the filter every year as you are just removing contaminants from the oil that the filter doesn't collect. 2012 TDV8 Vogue (L322)

Oil and filter changed a couple of weeks ago, just had to wait until the oil filter socket arrived.

 Encourage alternative fuels, use all the petrol!
2012 Range Rover Vogue 4.4 TDV8
2006 Mercedes GL420 CDI
2006 Porsche Cayenne Turbo S
2006 Jeep Commander 3.0 CDI with GDE HOT Tune
1997 Nissan Patrol 4.2 GRSE
1995 Vauxhall Monterey Diamond 3.2 v6
1994 Range Rover 4.2 LSE Beluga Black, Softdash, Brooklands Body Kit - Loved it!
1993 Range Rover 4.2 LSE ended up converted to 300tdi

Changed mine yesterday after 6k miles of mainly very gentle M-Way driving and no short trips. It was very thick and black so will probably be doing 5K changes from now on given how easy it is to do. not sure if I'm removing soot load from the last 6k miles or cleaning built up deposits from the last 138k miles.... 2012 TDV8 Vogue (L322)