The period beginning with the publication of principles-of-product-development-flow (2009), Reinertsen's magnum opus, through celeritas-publishing. This era represents the mature synthesis of his thinking into 175 principles organized across eight domains. Reinertsen's influence expanded significantly across multiple channels: david-anderson incorporated his queueing theory into the Kanban Method, dean-leffingwell adopted weighted-shortest-job-first into SAFe at scaled-agile-inc, eric-ries's Lean Startup built on his batch size and feedback concepts, and mik-kersten's Flow Framework drew explicitly on his queueing theory. His cost-of-delay framework became standard in product management.
His GOTO Copenhagen 2012 keynote brought the Flow principles to a large software audience. That same year, he co-authored six-myths-of-product-development and wrong-lessons-from-manufacturing with stefan-thomke for Harvard Business Review, bringing his ideas to a broad management audience. He continued teaching his "Second Generation Lean Product Development" seminar internationally, reporting that participants achieved up to 90% reductions in cycle time. Reinertsen positioned his work as "second generation lean" — a critique of first-generation lean product development that mechanically transplanted manufacturing tools without economic justification. He has also presented at the lean-product-and-process-development-exchange conference, where practitioners apply his frameworks alongside Toyota-derived lean practices.