Yes, it should take too long, but also there is sometimes too fanaticism about the Lean Startup theory. Too often people get stuck in the loop of testing and testing without really following a clear entrepreneurial idea. The risk is to end up building a nicely market-fitting product, but not a disruptive/visionary product.
Andreas Klinger described this amazingly well in his blog post "Why Lean Startup Sucks For Startups"... he wrote right after the Leas Startup Conference of 2013 :)
http://klinger.io/post/69794653694/why-lean-startup-sucks-fo...