Initially we just had the one, which worked ok for a while, but eventually it wasn't fair on DH because I was always on it at times when he wanted to use it. So we bought another which is now "mine". My course is delivered via distance ed, so everything is online, and that's the only way I can access research material, etc. And TBH it's partly a contingency plan, if one of them is going to die, you can guarantee it will be when you're only a few days out from some massive assignment being due.