It can only stay that high for so long. There is an end to every good thing. Of course it won't rocket down - it just can't get much more expensive.
I've got a bunch of my 401k in AAPL via a self-directed account - which has earned my son's future ~ $65k. I'm a bit concerned about volatility now -- especialy with Samsung and Google tablets hitting the sceen -- and plan to sell soon -- just need to identify a decent mutual fund to move the proceeds into. The handful of options ML's plan with our company includes are pitiful.