in my humble opinion, it all depends. and you have no idea how much i hate saying that. i mean we all are here to help right. so the best i can do is give you an example.
but before i do, if you are only talking about intra-day then there is time to consider as well as any profit target or trailing exit.
back to the example. when i started trading futures in 1997, i started daytrading in the fine market of live cattle. don't ask me why.
after about four months of ups and downs, showing a small profit, and trailing the stop. i was reviewing my trades in detail. i noticed that when i made a profit, it always exceeded $200 a contract. and even when i lost, i was usually up around $100 at some point before the fall.
so i started exiting at a $150 profit. regardless of what the market was doing, when i hit my $150 i fired off the exit order. keep in mind i was a small time futures trader with a $5k account. as the account grew, i added contracts so instead of one, i was trading 2 and kept this up until i was trading 5 at a time.
i was hitting around 7 out of 10. so i thought, hell lets try 10. and it blew up. i had hit critical mass for my entry/exit combo. i finally found the maximum contracts i could trade and make money was 6.
the point i guess that i am trying to make, is that exits are a function of your strategy and goals. where can you make the most money.
i no longer day trade on a regular basis. i use multiple profit exits. i have a minimum target i am looking for, a timed exit after the trade is in the money, a trailing stop, and a volatility exit. and then there are 3 exits on the downside.