Forgive me if this isn't the right place to post this, but onward... I use two identical WD My Book drives for TM and CCC. They are two and three years old respectively. Even if they continue to perform flawlessly, at what point should I consider replacing them just to be safe? I know that all HDD's fail eventually, but I'm wondering at what point I should replace a working drive for the sake of peace of mind? Know there is no hard and fast answer to this, but I just thought I'd ask for opinons. Thanks.