True, and I'm in one of those right now. Once you have enough in your account however you're better off handling the rebalancing yourself and using Vanguard's Admiral shares which have lower expense ratios.
What are the names of those funds?
VTSMX, VGTSX, VBMFX - with corresponding Admiral versions if you have enough money, which are the same funds with even lower expense ratios.
Edit: You wanted the rebalancing funds (those are the component funds.) The rebalancing funds are called "LifeStrategy" - see VASGX for an example.
There's also the "Target Retirement" family of funds. I'm currently in the 2050 fund, VFIFX.