I'm ordering an ottoman divan bed and need to choose between glides or castors. I was thinking castors so I can move furniture every few months to clean under it (it looks like there will be an inch or so gap under the bed, so it'll gather dust but I won't be able to fit the vacuum in). Every bed I see online seems to have glides as standard though, so I'm wondering if there's a good reason not to get castors? I assume they'll lock into place when we're not wanting to move anything?