Should I terminate my L-1 visa? If yes: how?

[joh.k]

Situation:
My L-1 visa is valid 2013-2016.
I worked in the US-based branch of my employer 2013-2014 (that's what my L-1 visa was made for).

Now I am back to the Europe-based branch 1.5 years before the expiration date of my L-1 visa.
I do not intend to go back to the US-based branch.


Questions:
1. Should I terminate my L-1 visa? (It is now still valid till 2016, but I am no longer working at the US-based branch.)
2. How can I terminate my L-1 visa? Can I simply walk up to a CBP-officer at the airport of departure and tell him to cross it out?

Thanks for your suggestions!