Depends where your account is, but an equivalent to VTSAX would make sense. If you desire some bonds, they should reside in one of your tax advantaged accounts. Bonds simply damp out the volatility of stock swings. If you can handle the swings, go ahead and keep your 100% stock allocation. But as you approach actual retirement, you will likely want to add bonds so that if the market suddenly tanks, you're not sitting there realizing that you have to keep working because your investments just dropped to 50% of what you expected.