If you're just going to throw it into a junk drawer I don't see any concerns about it. On the other hand, if it makes you more comfortable go to settings/my fire tv/reset to factory defaults. Or, if you're going to get some use out of it, just uninstall the app in question.
No, if you're not using the other device simultaneously it's not an issue. But again, simply delete whatever app you were using for access if that's your concern.Thanks, Mike. I don't think I worded my question well -- my concern is about the accounts. If I'm registered with Sapphire Secure, for example, and my account is for a single device used on one TV, I'm wondering if replacing the old Fire Stick with a new one will make it look as though I'm now using two devices/TVs.