9 years for me. Went all grain early this year. I'm very glad that I waited. There may be an argument for having gone all grain earlier, but I was able to get some very important techniques down to a science before I went all grain. Sanitation, bottling, kegging, secondary fermentation, clearing, etc.. etc.. etc.. All of that was second nature to me when i started brewing all grain. Of course I had to buy some new equipment... a couple of brew kettles and a cooler... AND I was able to read quite a bit about brewing and watched a whole ton of videos.
When I finally took the plunge, it was like I'd been doing it for years.
While the beer is better, I can't under state the value of the experience I got from extract brewing. I'm no brew master, but my beer is getting better and better with each brew. Having waited, I feel like the learning curve is nowhere near as steep as it would have been if I'd have "taken the plunge" a few years earlier.
And... the best part about brewing extract beer is... You get to drink beer.
One other thing... the very best part about being an established extract brewer is that you have a nack for brewing pretty good beer from extract. If you have a couple of empty carboys and just feel like you need to fill them, but you don't want an 8 hour brew day, you can fill them both in about 4 hours with extract. Shhhh... that's a little secret we'll keep to ourselves that the hard-core AG brewers don't know about. Expecially when they're drinking one of your beers and complementing you on how good it is. I still brew extract from time to time. 6-8 hour brew days are murder some times... especially when life and family gets in the way.