It will become a habit, so you have to decide if it's an okay habit for your dog to have. Also keep in mind you need to consider if it's okay for your dog to do it to people other than you. My guess is no. However, if you are working on bite inhibition (teaching the dog to control the pressure of his bite) letting him chew on you with little pressure (doesn't hurt at all, leaves no mark) can be a good way to teach him how to be gentle with his teeth. But once he becomes skilled at that I'd teach him that it's not allow anymore, or is only okay when you ask him to do it (for example, during a game of rough housing that you initiate).
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