If I think a pin is cute I almost always buy another, or a few...in some cases several. I don't collect Stitch, but when I see one that even I think is cute, I buy a few because they'll net me the pins I can't get (like new DSF pins).
Then there's the times when I sent out TA and more than one person replied with a yes, so I went ahead and completed both trades. (When mail was cheaper to send 😉)
Then there are the times when all of us (Coach and the kids) all wanted a pin, then one or more of us decide to trade ours out for something we want more. There's constant turn-over here - keeps it fresh, fun, new, exciting. 🙂
When I started out and had 'only' one page of traders I couldn't get anyone to trade with me, so I loaded up on traders directly from Disney and Disney Auctions, especially when they had a clearance sale. Many of the pins are now hard to find because it's been several years. I took a break for awhile and was shocked how well my pins were trading when I came back. Then I was really hooked and the addiction took full root and the kids got in to it as well. 😉
I totally think it's normal if they've been around awhile for them to have more than one of a pin. No worries.