When should you set up a data warehouse, anyway?

hey all, we're running a few apps now, and they're starting to make a lot of operational data. most of it's in postgresql, and we're doing some basic reporting right from there. but as the data grows and we want to do more complex analytics and business intelligence stuff, it's pretty clear our operational dbs aren't the best spot for it. when did you all decide it was time for a separate data warehouse? what were the pain points that made you finally go for it