i just started my 401k not long ago and have less then 5k in it.
Personally, you still have a long time in the market, 20 to 25 years. I would stick to S&P index funds, about 60%, 20% to 25% in a small or mid cap fund, maybe even a growth fund, and 15% to 20% in an international fund.
Obviously you don't want to leave anything on the table, but at 40, you've got to keep pushing the envelope until you max out your contributions for the year, and then consider other retirement savings options beyond that.
Maybe go up 1 to 2% every quarter until it hurts?