It's a difficult balance.
One one hand, it is clearly beneficial to take any good profit - especially when the other charts are indicating that the trend is poised for a change in direction.
However, FPM has a low percentage of profitable trades overall, therefore the trades that do win need to be sufficiently high to compensate for the considerable number of losing trades - sometimes exiting a trade early could rob you of an extra 100+ pips, which could mean the difference between overall net profit or loss.
Clearly, this method has been well designed and tested by its creator. By following the rules exactly, it has been proven to end up in profit in the long run.
However, it's a METHOD, not an automatic system. There are other basic TA techniques which I think can be applied in certain circumstances without trying to second guess the logic of the overall system.
For example:
I'm currently short on GBP/USD. I entered at 1.5621
It broke through the support at 1.5549 and then touched 1.5345, which is a significant trend line. At that time, it showed signs of continuing (all trend indicators were still showing a strong downward trend), however it has now bounced back off the trend line and is currently trading at 1.5468.
In hindsight, taking profit at the trend line would have been a wise move - 276 pips profit. Despite the fact that there were no indicators telling me to get out, the shorter trends were clearly moving in the opposite direction and we had hit a significant trend line.
At the moment I'm 153 pips in profit, and it now seems to be ranging. With no significant news planned today I'm happy to leave it open to see if it resumes the downward trend when the US session opens.
If it hits the resistance at 1.5549 and bounces back, I'll let it run. However, if there's a 4 hour close above the resistance I will take the remaining profit - should be around 72 pips.
If there were signs that the downward trend was coming to an end (as opposed to ranging) I would exit the trade now. However, that doesn't seem to be the case so I'll hang tight for now.
Regardless, I will be exiting the trade in profit
The problem with the 4H charts is that the exit signals DO come quite late, often 100 pips or more. However, provided your exit strategy is based on sound TA logic, and you follow the same principles for each exit, I can't see their being a problem.
It may be worth those of us who are currently using the method to post our trade entries and exits in this thread. Hopefully the sharing of the knowledge between us will help highlight the most consistent methods of exiting trades with maximum profit - which appears to be the key to this method!