[Retric]

TDD turns a 20 month (1 2/3 year) project into a 23 to 26 month project. Which is how I got 3 - 6 months behind.

And if your product does not ship for 6 months, then your first few itterations even if faster will also be behind.

PS: (3 to 6) * (1.15 to 1.3) = (3 * 1.15 to 6 * 1.35) = (3.45 to 8.1).

Edit: No wait it's 15-35% longer so (3.45 to 8.1) months.