True, I started as a complete ham-thumbed console neophyte (well I'd done some joystick racing on the C64) in early December, 1998, and didn't actually win the
Tuned Series until April 17, 1999. For a while I thought it would be the part of the game I would never win.
http://www.geocities.com/gt2toxs/gt/diary/1999-04-17.html
True, that was with a
GTO'95 MR, but I've won it lots of times with Vipers since then.
But anyway, I guess my honest answer is four months. My first documented Viper win in the series appears to be July 1, 1999, but I may have tried it before that.
But wait, there's more.
http://www.geocities.com/gt2toxs/gt/diary/1999-06-10.html
That indicates that I actually didn't win the
Autumn Ring race of that series until June 10, 1999. (And that was using a
Viper RT/10), so that makes my totally honest answer six months.