Leeks just grow well with about 5" of blanched stems, and a couple of inches of pale green leaves!
I reckon that a leek grown to have a 10" blanched length isn't quite natural, and after all, if you look at all the magazine pics of meals showing leeks, they're aways a light green!
I'm considering doing just a couple of buckets of them this year (in the past we usually grew about 200), and we'll leave it at that!
They're a fabulous veg, and I loved the organisation of all the beds, but as space is now at a premium, needs must..;0)