Well even a timeing chain should be checked at 100k-120k for signs of wear.... Any more then 5° of deflection and it is time for a new chain!!! If you replace timeing chain tensioner's and you still have timeing chain noise it is time to replace!!!! THe bad thing is that timeing chain's can last any where from 100,000 to 500,000 miles depending on design, materials used, heat treatment,oil used and oil change interval!!! You will find that today the trend is to use a single row timeing chain that is not a roller chain and that is very narrow and long.....These do not help with durability but they do reduce drag wich is a huge issue!!!