I think if you're going in a very long term trade a trailing stop will be better than a set take profit level because then you can trace the profits bit by bit till eventually you get stopped out. For example if you set a trailing stop of 50 pips and the trend runs for 1000 pips then goes down 100 pips then during those 1000 pips you will be cashing in every 50 pips (you stop will move in the trade's direction by 50 pips) till you get stopped out.