Normally schools shouldn't be placing deadlines on when you should accept/decline an offer. They are usually very understanding that you are still waiting for other decisions. Is this a very high-ranked school? Is it one of your top choices? I would try to talk to them, especially your POI if you can work out extending or removing a deadline. You CAN accept the offer and then decide to rescind your acceptance later for another, better offer, but you have to jump through some tough hoops, especially morally. Usually the school requires a written letter from you stating why you are changing your decision (they expect sufficient reason), and you have to send it to the head of the graduate program, you can't just tell your POI or a coordinator that you are no longer planning to attend. Of course, you can also discuss your concerns with someone if you are to accept, and state that you have been given an offer. If they want you badly enough, then they will work with you to make sure that you stay with them. Programs can be played against each other if they are competitive. Also, if you haven't heard anything from schools by mid-March, it is okay to contact them regarding the status of your application. At this point in time, I would communicate with your POI about your discomfort with the deadline.