So, I'm cold, so I'm thinking about things in a vain attempt to keep my head warm. And one of the things I'm thinking about is 4e.

So, for 3e, there was an idea called "E6", where you played 3e pretty much like normal, but you stopped gaining levels at level 6. Beyond that, you got a feat every x XP. This resulted in much simpler builds and was designed to hit and stick to the "sweet spot" of the game. Variants, like E10, were also suggested, but E6 was the original, to my knowledge. (I did one for Star Wars Saga edition called H1, where you were always a 1st level character)

If you were to do that to 4e, where would you stick your E? What would be the point where people stopped gaining levels, and advancing was now down to magic items and feats?