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system
should i set a stop loss for long term investments?
user
this is the exactly wrong thing to do especially in the age of algorithmic trading.  consider this event from 2010:  chart source  another similar event occurred in 2015 and there was also a currency flash crash in that year. as you can see the s&p 500 (and basically the entire market) dropped nearly 7% in a matter of minutes.  it regained most of that value within 15 minutes. if you are tempted to think that 7% isn't that big of a deal, you need to understand that specific securities will have a much bigger drop during such events.  for example the powershares s&p 500 low volatility etf (splv) was down 45% at one point on aug 24, 2015 but closed less than 6% down. consider what effect a stop loss order would have on your portfolio in that circumstance.  you would not be able to react fast enough to buy at the bottom.  the advantage of long-term investing is that you are immune to such aberrations. additionally, as asked by others, what do you do once you've pulled out your money.  do you wait for a big jump in the market and hop back in?  the risk here is that you are on the sidelines for the gains.  by missing out on just a small number of big days, you can really hurt your long-term returns.
assistant