It's hard to say whether the Asset Allocation Fund portion will help or hurt the performance of VASGX. This depends on the results of the fund manager's decisions. In my opinion, you're making a good investment in VASGX, especially considering your time horizon. Vanguard isn't going to take large overly-risky (besides stocks being inherently risky) investments within the fund. They will move a portion of the holdings into or out of stock funds depending on the outlook of the world economies.

This fund is a good core holding. Dollar cost average and over time you won't be dissapointed.