I think if you pay and you don't go you wasted your money. I know that the schools know where else you are holding spots at in April. If they find out, they can rescind your acceptance depending on the school. My school doesn't require an April deposit though or maybe I didn't get the request yet
You must submit all the deposits by the date they are due in order to attend a school. You may place deposits at any number of schools if you want to hold multiple seats. In April, the schools will share their list of students with deposits down. If you hold spots at more than one school, they'll contact each other, decide who gets to send you a letter/email and tell you that you have until some date to withdraw from all but one school... or else they all rescind.
paying the first deposit holds your seat temporarily. paying the second deposit means that you're going to that school for sure so the seat is yours 100%. you can withdraw at any time, however. you just lose your money.