if its a quality built tank, then you would expect at least ten years out of it, as long as your not abusing it, (like leaving it outside in the snow for storage), you should have no problems ever! Silicone that is used nowadays is great stuff! a tank that is used for what it was intended to be used for should last 50 years+ no problem. if you want an excuse to buy a new tank youll have to find a different reason, like "I deserve one"