when i worked at peugeot we used to change them every 4-5 years or 72k if i remember right on 2.0 hdi although we aways ended up changing half them early due to leaking waterpumps!
used to be able to change them in half hour 45 mins and the book time used to be 4 and half hours,all that extra money i used to put in the dealers pockets, what a mugs game eh spending years how to fix cars to end up waving a pole about spraying magic water and earning double the money i did there!!