We have a placeholder booked from our March cruise and wanted to use it on a cruise between Christmas and New Years in 2024. Our TA is telling us that the cruise we want has a black out against using placeholders. Is that a thing?
Yes, it can have such a restriction. You should be able to see it in the fine print of your placeholder cruise paperwork or online.
Per DCL site, there are lots of blackout dates for almost all of their ships.