How long does it take to create a product vision?

• For any Product, the hierarcy, in terms of immediate to long-term is Execute -> Features -> Roadmap -> Strategy -> Vision
• The focus for any product team should be to execute & launch and then working on the features & building on the roadmap from a bottoms-up perspective. They should also embark on a top-down appraoch of understanding the market landscape, the user problems they can solve profitably and setting the vision. The intersection of these approaches can take anywhere from a few weeks to a few months to a few years and depends on the stage of the firm, the product, the type of company and the lifestage 
• For start-ups, Vision trumpes everything else and would be required before they raise capital, attract talent or are able to build. Tesla is an excellent example here. 
• For large firms, product in market thats generating revenue trumps everything else and they have the chance to stumble upon a good strategy or vision if they keep iterating. But, this isn't a given, most firms stumble & fall rather than pick themselves up & iterate. Chevy has the vision laid out for them by Tesla but they haven't been able to take the Bolt to where Tesla is. 
• For other firms, the answer lies in the middle of the specturm. PoleStar & Riviian are able to ride on Tesla's coat-tails, Toyota continue to follow their incremental approach with the Prius but it feels like an opporunity lost, BMW & Merc have launched incredible electic cars that feel like the future, etc

It can take anywhere from a few goals to multiple weeks. In addition to the thought that goes into it, its important to align stakeholders to your vision and this can add time to this task.

This really depends on the organization, the stage, and how much detail you want to include in your vision. I'd say if you're just starting out, it's much more important to just get something down on paper that you can then iterate on as you go forward. I'd say if you're a mature company, really thinking through where you want to be in five years, this is something you should spend a lot of time on and you should take to review with a lot of people. So there's no simple answer. I think it really just depends.