I too am a fan of VWINX. In fact, if I could only own one mutual fund, that would be the one. That would be especially true if the fund were in a tax-sheltered account.
But be aware that VWINX holdings are about 60% bonds, mainly intermediate bonds. When interest rates decline, those bonds appreciate and the fund makes good money. That's been the case in the last 5 years.
But if interest rates rise, and especially if they rise rapidly, this fund will take a real hit.
I'm not arguing against this fund! VWINX gives you more return than a money market fund or a CD would, but there is more risk, and you should know that.
If the risk bothers you, consider dollar cost averaging into the fund: instead of putting all your money in at once, send Vanguard a smaller amount each month.