Index fund portfolio - investing questions?

I have a regular investment account (I am already contributing to a 401k and Roth IRA) which is composed of index funds. Should I stick with just 1 index fund and keep feeding it monthly or should I buy multiple index funds and allocate accordingly?

The money is not needed for 5-10 years and may be used to pull out cash given sizable gains.

index fund only invests in those stocks which represent the index and in almost the same proportion as the stock is represented in the index. So returns of index fund is almost in line with the returns on index. So diversifying your investment in different index funds will not at all increase the chance of better return. Also it will raise the additional work of maintaining different fund.

If u need to diversify, invest in different type of funds, like equity, mid-cap, real-estate funds, gold funds etc.

I would suggest about 70-80% in a domestic stock fund such as the Vanguard Total Stock Market Mutual Fund, which will optimally diversify you domestically. Then put ~20-30% in a Foreign Index Fund. Depending on your age, you may also want to but some money in a Bond Index fund.

Copying the Target Retirement Funds at Vanguard may be a consideration. For funds not in a tax-sheltered account, I don't recommend actually investing in the Target Funds as they are tax-inefficient.

If I were you, I would diversify a little more. I would pick 3-4 funds that are a little more risky than index funds since you don't need the money for at least 5 years (not too risky since 5 years can fly by)...

I would pick some a mid-cap growth fund, a natural resource fund, and an emerging market fund. Something along those lines that will give you a little more opportunity for gain (with some added risk!).

Good luck!