After fixin hundreds of failures, it is my conclusion that proper maintenance would be to replace the upper rails every 4-5 years or 50-75k. Do what you want with the chain and tentioner.
The problem in 90-100% of the cases is the fracturing of these rails with the pieces going between the gear and chain jumping teeth till it bends valves.
As to the tentioner, there is a check ball inside that retains the oil to maintain pressure. Even brand new tentioners can have that check ball leak occasionally and the short rattle that then occurs is what gets the rails. The rattle CAN NOT be permanently prevented. The ONLY prevention is to remove and replace the rails before they become brittle so they can do their job and contain the rattle when it happens.
Other than removing the pins, the rails are an easy DIY job, with gaskets it can't be more than $30 in parts. The rails are less than $5 a piece and there are three although the two in the left head are what cause most of the problems.
You can make the job more expensive but you will get little in return till maybe 175-200k.
Bosch Master, ASE Master, L1
33 years MB technician