Framesira/Shutterstock Like any other wearable or electronic device, Fitbits — just another  another company owned by Google  – will eventually reach the end of their lives. This means it's time for a replacement, which you'll probably want to get anyway, to take advantage of the latest and greatest features and improvements. But how do you know when your old Fitbit needs to be replaced or when there could be a potential fix? If the screen is blank or flickering, it's not charging. If it keeps rebooting itself, this is a good sign that the wearable is on its last legs. But there are a few tricks you can try before tossing it for recycling and buying something new. It could be a software issue, for example, or maybe it's the charger that's the problem, not the tracker or smartwatch itself. Even if you plan to upgrade, these tricks can help keep it going for at least a little while longer while you search for the best deals on a new one.…