I see BIB, Petey_C and Sixer as all having strong points.
I'm going to lean towards the "It's not the GC's business after closing/final" position with a couple of notable exceptions.
1)If you have a good relationship going with the GC and your getting a lot of work it would be foolish to do anything that could be construed as disrespectful to said GC whether you see it that way or not.
Of course if it turns out that the GC wants to mark up your work at that point the owner might just find another electrician. Now you have somebody else hacking into your work that you're expected to warranty.
That brings me to:
2)Warranty issues. Lets say the drywallers didn't do a very good job of getting the lid hung. You go crawling up there and shake something loose. Cracks start to form soon thereafter. Homeowner contacts GC about warranty. GC claims you caused cracking by scuttling about in the attic and won't even consider the possibility that the lid was improperly installed.
It could take a long messy conflict to get that situation resolved.
It doesn't seem worth the trouble either way if the GC is going to be that way about it.
Fortunately, my "hanyman" GC's (a few to a few dozen homes a year) wouldn't take that position in the first place. They would put the owner in touch with me and be done with it.
