As long as you like! Your reservation with Babylist will never expire. We do ask that you return to your reserved gift list and mark the item as purchased after you have bought it. You can indicate what store you purchased it from and, if it was an online order, enter the order number. That makes it easier on the registrants in case they need to make any exchanges.
If you change your mind, return to your reservation page with Babylist and click the blue "Cancel Reservation" link in the item's box to put it back on the registry for someone else to purchase.