It's weird how this justification for "look a bubble!" has been consistently voted to the top of HN for its entire existence. Smart people have been chatting about their being or not being a bubble longer than Hacker News has been a thing.
I would say for most areas it was less than half a decade. I can't think of many sections of an economy that can see greater than 20% year over year growth for more than 5 years without repercussions... Without corresponding growth in other areas to compensate, it's just not sustainable.
> Is 'Web 2.0' Another Bubble? (2006)
[1] http://www.wsj.com/articles/SB116679843912957776