I'm going to make a guess here. I run a Seagate USB2 drive with my Poser runtime and a lot of other stuff, and it's running 24/7 without problems. But it's sitting on a shelf with plenty of airflow, and this room is cooler than I hear of some offices in the US. And it doesn't get moved about. Also, a good-quality USB lead. If you're working somewhere warm, or if you move it around a lot, I reckon you could be at higher risk of problems. A lot of the big external drives are not, I suggest, a true portable solution. But they're a good way of adding a large drive to your system.