I wouldn’t agree here, because my experiences showed me that in 1-2 months you can know if you are going in the right direction. Of course you can pivot later, but if I do customer research and interviews properly and execute fast with MVP that I can charge for, I can move forward or throw idea and focus on the next one.
They pretty much preach in YC that it'll take 2 years to really know if there's something there. Of course it can happen sooner. But the advice is not to quit before 2 years.
Coinbase founder, Airbnb founders, Rippling founder all preach this