Like wearing a T-shirt only once for every new day, and then never use it again.
Yes, but there's nothing wrong with wearing a brand new T-shirt everyday and throw the old away, if it's for free. In fact, it's even better.
If this happens (although I know mathematically is almost 0) where do the bitcoins go? To the first wallet that created the address or what?
The bitcoins don't move across wallets. They remain in the same location, which is the blockchain, inside blocks, as outputs. If you have the private key to mathematically "unlock" such output, you can spend the coins.
To answer your question, the bitcoins will appear in both wallets.