I wouldn't worry too much about "hoarding" offers. It's your life, not anyone else's, so don't make any choices until you are ready. Obviously, if you know that you won't accept an offer, its best to let it go sooner rather than later. But, if you have multiple good offers, keep them until you've made a decision that you are comfortable with. All programs (in the U.S.) will give you until April 15th, so if you make a decision in March that should give programs enough time to reach out to their waitlists. In fact, this is exactly why there are waitlists, so that you can have time to make decisions without it harming others.
And with my offers none of the committees have asked me to commit sooner than April 15th, just to let them know as soon as I know. I've just told them thank you and that I will be strongly considering their offer.