My wife and I arrived last Friday morning around 11am, and we were unable to check in early. We had a Deluxe room, and there were none available at the time. They were happy to keep all our bags in their storage while we went out. When we came back later in the afternoon, the room was ready, and all our bags were waiting in the room for us.
One other point...the front desk agent gave us an executive lounge key (being Diamond), and we could have lounge access even if our room was not ready.