Peter,
I can answer only for myself.... I open them as I open all my stuff(with the exception of a certain red Custon Ferrari in BP - I have like 22 reds loose, why open it?) that I am going to keep. Cash Cow? well, maybe, but I buy and open for me... if I buy to sell then I don't open.. if I buy for me, then I open and don't really care what the market does..... it really isnt ALL about money you know. If times got really tight and I had to sell all my cars, would I wish they were all in BP and mint? Yes. Would I regret opening them so I could actually handle and enjoy them? Nope, sorry, life's too short.
Do I wish I had a couple of those Camaros - yes and moot point...... if I had them, yes... if they came in Sherry's order wouldn't matter, would it?
I keep a few cars hoping that someday they will appreciate, but not too many. I spent waaaay too many years killing myself trying to get all the "special" cars and the hobby lost the fun that I started out with. Now I just get what I get and enjoy those
Rob