We can't nswer this question for you. You need to ask yourself, can I afford to lose access to those 250 sites for a day or so if my concentrator dies. I would think probably not. If the answer is no, then it's time to get a backup.
As to where it should be located, again you need to look at your environment. Certainly put it on a different power supply, but if it's at the same site and connected to the one Internet link then if that goes down you're still hosed. Ask yourself, how important is this to my business, and does the expense of a possible multiple-hour outage outweigh the expense of putting this box at a different site with a differnet Internet connection.