I found this Exploit a few years ago with another WoW Celebration Package (this year's: Celebration Package - Item - World of Warcraft). As it still works with the Package of this anniversary I am going to share it with you.

Normally, if you loot your Celebration Package, the Package gets destroyed when you log off or in, idk. But there is a trick on how to keep it.

You simply need some kind of wrapping paper (e.g. Red Ribboned Wrapping Paper - Item - World of Warcraft). Wrap your Celebration Package. Now you can send it via ingame mail between you charakters. It does not get deleted, when the package is in the mail, however it will get deleted, if you log off and have the package or the wrapped gift in your inventory.
Simple guide: Loot Celebration Package on charakter, that you want to get the buff on and unwrap itUse the buffRe-wrap itSend it to another charakter (note: you can also trade the buff to friens like this)RepeatBenefit" +11% Kill experience and reputation from kills

Note: If you don't have the Package on your main characters anymore, some twink might still have got it. Or maybe a friend still has it and can trade it to you with this method.

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