In my opinion ... a company cease to be a "startup" when several of the following are true:
- no longer running on funding rounds (ie, they're now profitable)
- no longer doing "major" new product development (not the same as not investing in R&D, new products, etc)
- mature into a "traditional" organizational structure (less "seat-of-the-pants", more "plan-and-execute")
- older than 10 years (though some startups transition at 3 years, and others might take 20...a decade seems a plausible age cut off)
- "adults" are running the place (this is not exclusively an age determination; more of a managerial/employee maturation indicator)
- no longer trying to "do the impossible" (beat MAGNAF, displace Uber, disrupt government...) - rather, working towards being "good" at what they're "good at", letting everyone else [more-or-less] alone
