Many investors are forgetting the all important rebalancing chore:
Rebalancing every quarter is unnecessary. Once a year is often enough. Most people can 'rebalance' strictly by buying underweight components with new contributions.
My Own Advisor - My blog about saving and investing my way to financial freedom.
I made the rule, currently, of rebalancing once every 4 years, while using new money to do my best to balance. Its easier with less money. The idea is just to allow things to run their course in the market.
Studies who rebalancing often (once a year) is more beneficial in a bear market. Not rebalancing is better in bull markets. I'm not timing, just trying to find an objective middle ground.