Probably quite a few, in broad terms. Brian McLair for example went south too early to aston Villa and ended up back with us. Alan Martin thought he was a much better keeper than he actually was and after hawking himself around English clubs he ended up at Ayr and now QoS. More recently, Fraser Kerr, came back to us from a stint at Birmingham City. Another example is Robbie Leitch - where is he now?
Going back to the original question of whether its better to jump ship early for big money or to wait, a year or two, to mature, posters on this board have already answered that. Some good posts, but it depends entirely on the individual. For some, leaving early is good for others its a bad move. It depends on a young lad's maturity, character and personal circumstances. Leaving home at 16, 17, 18 or even 19 is a big move for anyone and some can't wait whilst others are very loathe to leave home and familiar surroundings. For some money is god, for others there's more important things in life. I've known several excellent and very well thought of colleagues in my career, who could easily have risen up the career ladder but had no interest in doing so because they didn't want extra responsibility, pressure or to move away. At the other extreme I've come across others, with lesser talent, who didn't care who they trampled over to gain a few extra pounds.
In short each to their own. For some young lads its better to stay a year or two; for others its better to leave early for more money down south. I'll end with advice I was given and many of you may have been given also "Be nice to folk on the way up as you might meet them again on the way back down."