You can open your position and let it open as much as you want, it's up to you but you have to know why you are doing it and you have to know when you close it and this depends on your trading system and your vision to the market and I also have one position in Euro / USD since November last year. I'm still holding. because I believe, one day it will definitely rise again. difference, the account that I have is swap free. most importantly, we still have a large margin. there seems to be no limit to how long we can let our trading position remain open. My experience has opened trading for 2 months and closed it after profit, so there was no problem.