Good question, makes me think since I'm at 8 and likely will add another one in a year or so.
This gives me time to order my pins (I like them all) so I would have to find some way to cut the weaklings.
I think it's best for me to start with my favorites
Met pro
AcDc premium
Tron
IM
STLE (kind of on the edge because I'm not in love with the rules).
would have cut
Tspp (mainly because this is not like new condition). If it was 'like new' I probably would trade this with STLE.
Potc
XMLE