Portfolio weighting based on different time horizons

[Kilbim]

Hi All

I was wondering how one can weight it's portfolio, and thus diversify it's assets in the best way, when he has different time horizons.
The easiest example would be money you invest in your retirement account (so for 30 years from now, for example) and money you invest to buy a house in 15 years.

How do you weight one and the other when looking at your overall portfolio (for example to be sure you aren't too much invested in stocks, regarding to your risk tolerance)?

Thanks

[dividendman]

I think the easiest way would be to read about Vanguard's target date funds, just google that and read up on it.