2.0 hdi oil change miles / effects of old oil

hi blingo lovers/haters  (i'm both, depends on the day!).

i read recently that it's best to change oil every 5 or six thousand miles? crikey, seems a lot of oil changes for a busy driver!

also - my beloved/hated blingo failed on emissions today (i'm in spain) - tester said i should change oil and filters as old oil / dirty engine can cause higher emissions..

is this a good suggestion?

thanks.