Until he longer fits comfortably.
You didn't mention how big he is or what size crate he's in, so it's impossible to say. Halo stayed in her shipping crate for at least a few weeks, maybe a month or more, and then moved up to an intermediate Vari Kennel. Keefer was a bigger puppy, so he went right into the intermediate size. I think he was maybe 5 months old or so before he moved up, but I can't remember for sure. Halo was quite a bit smaller, so she didn't outgrow it quite as quick.