Buy and hold: It may not be new or exciting, but it's reliable, and it'll get you where you need to go. It's the Toyota Camry of investment philosophies.

Buying and holding is an excellent strategy for most investors, especially for most long-term accounts, retirement or otherwise. Buying and holding allows investors to save a small fortune in fees. More importantly, as many investors would rather watch paint dry than spend their leisure time managing their money, buying and holding ETFs (which by design track certain market indexes) can be a winning strategy for hands-off investors.

The case for mid-caps

Buy and hold: the Toyota Camry of investment philosophies, made even more exciting with the bold use of beige. Source: Wikimedia user IFCAR.

Large-cap stocks always garner a lot of attention because they are the companies that are most visible in our everyday lives. There are piles of historical data relating to large-cap performance. Small-cap stocks, on the other hand, are attractive if an investor can stomach the volatility because of their high earning potential.

Mid-caps, however, often go overlooked when compared to their larger and smaller counterparts. Mid-cap ETFs, however, have outperformed large-cap ETFs in the last one-year, three-year, five-year, and 10-year periods. While small caps usually outperform mid-caps in the long-term, mid-caps offer less volatility.

For investors who have a long time horizon, tipping your asset allocation in favor of more mid-cap exposure may strike the perfect balance between volatility and return.

Consider these 3 mid-cap ETFs
Schwab U.S. Mid-Cap ETF
(SCHM 0.30%)This fund is a top pick for investors who are looking to add more mid-cap exposure to their portfolio. Nearly 93% of the fund is allocated to mid-cap stocks, with the rest allocated to small-cap stocks. This ETF is a tremendous value with a 0.07% expense ratio and 25% turnover. Because of its relatively pure asset-allocation, this ETF would be a good candidate for investors attempting to assemble a simple, long-term portfolio of three to five ETFs. This ETF is also a good candidate for investors attempting to replace large-cap ETFs without gaining too many duplicative holdings.

Vanguard S&P Mid-Cap 400 ETF (IVOO 0.17%)This fund is an excellent choice for investors who can handle more volatility. The Vanguard S&P Mid-Cap 400 ETF has 75% mid-cap holdings and 25% small-cap holdings. The additional small-cap exposure will increase the fund's overall return in the long-term. Investors should be aware that greater small-cap exposure usually results in additional volatility, however.

This ETF is also an excellent value with a 0.15% expense ratio and an exceptionally low 10% turnover. Investors should note, however, that this ETF trades at a volume approximately one-tenth of the Schwab U.S. Mid-Cap ETF. As with any lightly traded ETF, investors could be hit with giant bid-ask spreads.

iShares Mid-Cap Index Fund (IWR 0.34%)This fund is a monster with nearly $9.4 billion in total assets. iShares Mid-Cap Index Fund is much more liquid then Vanguard S&P Mid-Cap 400 ETF, which means investors need not fear a giant bid-ask spread. This fund is ideal for investors who already have exposure to the Russell 2000 index and are looking to add more mid-cap exposure.

Investors should be aware that this fund has a lot of exposure to large-cap stocks, which are weighted at 31.62%. Investors with a large amount of exposure to S&P 500 index funds will find that this fund has a lot of overlap. Investors looking for this specific mid-cap exposure, however, will appreciate the reasonable fees of 0.22% and a low turnover of 13%.