[GMcL]

I don't think it is a waste of time if you are planning to keep the car going for as long as you can.
My old S60 D5 which I sold in 2013 is a 2005MY car. Looking on the MOT checker it has passed the latest MOT with 218,000+ miles on the clock and still with only one advisory in the whole history - 2007 when I left the satnav stuck to the windscreen.
My current 2011 S60 D3 will run until it is legislated off the road. That engine will never wear out with regular maintenance, it only revs to 3,500rpm