Do not accuse me of being a hypocrite. Since my article, An ETF Asset Allocation Plan for Everyone, I have bought a large number of shares in DEM, VTV, VWO, and EFV. And I will hold those funds in those ETFs ad infinitum. One thing to keep in mind regarding asset allocation with passive funds–make sure that you take into account any active funds you have or any individual stocks when deciding how to allocate. I personally own a large number of US small-cap and micro-cap value companies (examples include TSRI, MSI, SCVL, and LAD), so I do not need to duplicate that with ETFs. On the other hand, I own only one foreign stock, so I needed to drastically increase my portfolio weighting to foreign and emerging markets.
One advantage of using ETFs is that they are tax efficient. Also, if an ETF shows a loss towards the end of the year, an investor can always sell the ETF and buy back a similar one (although check with your CPA on this). That way an investor can reduce his or her taxes while avoiding the wash-sale rule. Of course, this should not be done unless the tax savings would be large, because commissions and bid/ask spreads can eat up gains from this strategy.
Disclosure: I am long all the stocks and ETFs mentioned above. I am not licensed to give tax advice: please consult with your tax attorney or CPA regarding legal tax avoidance strategies. I have a disclosure policy that is based in the tax haven of the Jersey Islands. It is also Amish, but only so that it can legally avoid paying social security taxes.