Why specifically 3 funds? What kind of assets do you want to own underneath the fund? What is the long term goal of your portfolio?
These are the questions I would ask. Personally my long term goal is to match market performance and diversify away from extreme volatility, and minimal cost. So I have some sort of low cost index fund (i.e. S&P 500), low cost non US stock fund (international index, gold, short term bond but not in fund), and then dollar cost average them regularly. Then leave some extra cash on the side to take bets on companies in industry I know well to time the market.
So far I have been doing pretty well. Just make sure you have some stuff you can sell during retirement if you need to start withdrawing for living expense (hence most advisors recommend bonds in there), so you can sell something stable whether the market is up or down, so you are not forced to sell at a loss.
One thing to mention: everyone has different financial situations and need. I actually anticipate to make more money in retirement due to compound gain over the years, inheritance, and my own financial discipline in my early days, that my investment horizon is more for passing on to children. If you have family history of certain disease and you anticipate to live a lower than average life expectance, with health problem so you can't retire late (I plan to never retire and work till the day I can't anymore), you may need to plan the withdraw amount and schedule very differently. For me I may not want to put much other than company match in 401k so I have more working capital to time the market, that may not work for you.