When to do a carbon clean?

Quick question for the experts on here:

At what intervals should a carbon clean be done? I bought my 2009 S6 a little over a year ago with 35k miles on it. I am now at 59k. The only carbon clean that I know of was done at 15k, according to carfax.

The car runs great, no noticeable loss in power since I bought it, and still gets pretty decent mileage (for what it is) at 16 mpg on my commute and ~20-21 mpg highway on longer trips.

From what I have read, I have seen suggestions of performing a carbon clean every 10-15k. With no obvious symptoms - I am hesitant to break it open and perform this service unless I will see some real benefit from doing so.

Your thoughts?