if you buy a second hand car, its the first thing that should be done, regardless of "indicated" milage.

100,000 km or 48 months i think it is.

Do both valves all 16 and belt regardless and while at it chuck in the pistons and rods ect ect im spewing i didnt do it at first or second time but still making enough power till it reaches the 400 , maybe.lol