Every quarter I'd think. If you can't stick around for the quarterly numbers to pop through and then get punishment or reward, then you'd be a job hopper. If/when we change to a sub quarterly financial system, then the job hopper meme would adjust to that as well.

But there's no way you could do any big project in a quarter.

Who says that you need a big project done to get a new job? It just has to LOOK like you did a lot of work.