This is a tough one. So here are 2 different things that my DH and experienced. We wanted to make a reservation about 4 years ago or so. We wanted to pay for the deposit with a check, rather then a debit or credit card. So we told them we would be sending in a check and they said they had 2 weeks to send in a check. We ended up paying with a debit card b/c they said that the turn around time for sending a check to applying it to your reservation could be up to 30 business days. But in theory, they would "hold" the reservation for two weeks as they waited for a check.
The 2nd situation was when I was booking tickets and a room for my mom and I. I was told by the cast member she would hold this "deal" that popped up on the screen. It was a room only deal and we would be paying for our tickets separately. I needed to contact my mom to confirm so I hung up, spoke to my mom, and called right back to book it. Oh my goodness, the hoops we had to jump through. There was "no" holding they said when I called back. So basically we lost it. I did end up getting it back again but we had to talk to the supervisor and go through huge hoops. This situation is a bit different b/c we were wanting to book a special rate that popped up that some time you get when talking to a cast member and you don't book right then and there. Its an offer that the computer generates and isn't really an offer for everyone. But the point is, the original cast member said she would "hold" it and she didn't/couldn't. And b/c it was a special rate, I couldn't just "book" it and send a check. It needed to be paid in full that moment. So if you really want to book something, then just book it.