I think the whole “Torro Rosso as feeder team” idea is working out just as well as the Young Driver programme is for Red Bull – ie not at all. It’s produced Vettel, who got his first stint in a BMW, and every other driver has been a “throw them at the wall and see if they stick” job, with the exception of Buemi, who has been in the team two years, and showed – errr. Hmmm. Not a lot, really. Certainly not any sort of progress.
The McLaren Young Driver programme generally goes for one driver a year, as far as I’m aware. Even at that, they don’t hype it too much – it’s a way to keep involved in lower formulae and evaluate talent at close quarters as it develops, as opposed to the Marko Method of forcing talent where you think it should go whether it’s ready or not.