I'm also interested in this topic. I got about 2,500 on my 335i sport and I'm thinking I'll pay for first one in spring.
I've read allot of threads on this and what I got out is.... There is no harm in doing it. But there COULD be harm if not done. I don't think anyone has any solid proof and mostly it's about what makes you feel better.
So, for me little money is worth it. Otherwise I'll wonder if I should have done it if something goes wrong later. BTW, I'm wanting to keep this for a long time. If you are not then don't.
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