Some of us have had what appeared to be a issue with the Lock Tumbler turn out to be broken parts inside of the Steering Colum Lock Assembly.
A year and a half after I replaced the Steering Colum Lock the Lock Tumbler fell apart.
I installed a Meyle Tumbler in mine and have been driving with it for a year now. However, that is not a good test because when I installed the new Steering Colum Lock I fixed it so that it does not lock the Steering Colum. That means when I turn the Key I don't have to turn against Steering Colum Lock Plunger Spring.
I was at a locksmith's shop and overheard a conversation where the locksmith was telling someone that hanging a large wad of other keys from your Ignition Switch Key shortens the life of the tumbler. The extra weight is bad for the Tumbler.
My steering Colum Lock thread
http://www.peachparts.com/shopforum/diesel-discussion/333785-steering-colum-lock-ignition-lock-housing-causes-ignition-switch-failure.html