An otaku would say there is no such thing, while a casual anime fan would probably give you a more conservative answer. As diverse as all anime shows are, so are its fans, and each one would have a different response to this question. And the interesting thing is, all of them would be right.
There is no one answer to how much time watching anime is too much. However, there are a few fluid rules to follow, so you can enjoy as much anime as you want without compromising other parts of your life.
Rule #1: How important is anime in your life?
The degree of importance anime has on your life would depend on whether you are a hardcore anime fan or a casual watcher. If it is your only source of entertainment, then your overall wellness most likely hangs on your ability to access your favorite anime shows on a daily basis. In contrast, the more relaxed a fan would be, the more disappointed or irate he is if unable to get his regular dose of anime.
Another way to distinguish where you are in the fandom spectrum is by answering the question: Do I want to watch it, or do I HAVE to watch it? If you are leaning towards the latter, then you have equal parts of blood and anime flowing through your veins.
Rule #2: Spend only your spare time watching anime
Some spend 1 to 2 hours a day of their time watching anime, while others watch until the wee hours of the morning. Either would be fine as long as you are still able to function or behave normally the next day. Others watch sparingly during the weekday then binge-watch at the weekend to catch up. Again, this is OK. As long as you have time for school, work, and other priorities in life, then you are good to go.
The key is finding out how much time you have to spare every day or every week. It would then depend on where anime lies in your list of priorities and how much of your free time you would spend on it.
Rule #3: Is watching anime getting in the way of you living a normal life?
This rule is mostly applicable only to the extra milers when it comes to watching anime. Some people can binge-watch an entire series in one sitting. Online streaming has made it possible to skip the opening and closing credits, blurring the lines between each episode and making it feel like you are watching one very long movie. Others can go one step further, watching more than one series continuously.
Some even more dedicated anime fans can take binge-watching to a whole new level. They are informally referred to as marathoners and ultra-marathoners. By watching anime virtually non-stop for a time, it enables you to appreciate the whole series without missing or forgetting some subplots or backstories.
Whether binge-watching or marathoning, it is fine as long as it is planned. You could treat it as a one or two-day vacation away from your worries or responsibilities. It is your free time, and only you know the most satisfying way to spend it.
Is it a case of superabundance?
Whether you spend too much time watching anime or not will depend on your personal situation, your distinct preference, and your unique personality; the answer is within you, and no other person can tell you otherwise.