Hi buddy,
I wont say I'm an expert nor any body out here is (except Teak and Gates85) However most of us has a pretty good 'know how' of the subject since we have taken some time to research on the internet and relevant books, you could be rest assured if we know about it we'll answer,if we dont we prefer letting it go, instead of providing false info.
Your result is 99.9% conclusive(test generation and type doesn't matter at this time frame),there's no much difference between a 12 week and a 13 week test since an average would sero convert about 22nd day after the exposure and the rest sero convert within 4 to 6 week, keeping that in mind detectable amount of anti bodies would always develop after the sero Conversion phase
so having said that 8 week test should indicate a strong result however a conservative approach '12 weeks' result is conclusive.
You're safe, go party :-)
Regards
Mike
In case you'd still wanna go for an expert's insight on the same, you could shell out 15 bucks outta ya pocket and ask Dr. HHH but i'm 100% sure there would be no difference in the end opinion.