Every 3 hours. But also, if you have API access you can use the OpenAI playground to query GPT-4 as much as you want. Sure, you pay a cost (per token), but if you're willing to front the bill you can move pretty quickly.
Indeed, if context lengths grow to millions of tokens, and prices are cheap enough, I could see users feeding their entire codebase in to ask a simple question about it - or feed in every email from their inbox to find something specific they're looking for, or use as style/content guides to write a response.