I will not give advice but I will tell you what I did & what I would do again if I had ten or more years till retirement.

What I did,,,

In 1991 I invested as much as I was allowed in a deffered compensation plan (like your 401 K). I invested 100% of that money in this fund, T Rowe Price Mid Cap Growth. After about 3 & a half year I cut way back on my input & just let time do the rest. It has grown to over 5 times the sum total of all the money I put into it. Last Summer when the first whispers of foreclosures on sub prime loans started coming in I moved 95% of this position into a bond fund. With in the next week I will begin to move it back over to the mid cap growth until I have 95% back in this fund.

What I would do,,,

If I had about 10 years till retirement I would invest as much as I could in this fund & let time take care of the rest. Over the past 16 years T Rowe Price has had one of the best performing mid cap funds there is.

Hope this helps answer your question.