Just a heads up, should you not use the placeholder after 2 years, Disney will refund the placeholder funds to the original form of payment. I had hoped to be able to cruise Disney again so placed a placeholder on our last cruise but I'm just priced out of Disney so they credited my original form of payment. It ended up being a closed account but I was able to work with my bank to get the funds transferred to an active account.
All this to say, if you use a Disney gc and there is any chance at all that you won't use the GC, be sure to hold onto it as that's where the refund will be applied.