Service question

[Bdiesel570]

So I have owned a few Rolex models in the past, however I always flipped before it needed service.

I just got a 2013 BLNR last month from DavidSW which I don't plan to ever get rid of as it is such a stunning piece. I have been testing its timekeeping ability with my phone app, WatchCheck and it is keeping anywhere from +1.6-2.7 seconds a day with an average of +2.1.

I am extremely happy with that, the question is do I send it for a service once it goes out of COSC? What do I look for?

Thank you. Again I never send one in for service so I don't know what to keep my eye out for.

:)