If you have enough money according to your lot size then you can stand your position as long as you want but for it market movement is also important. If you trade according to the market trend and trade after the analysis the news, follow the good indicators then you can stand your position long time. You can keep your position until you earn a profit on month, six month and one year, no time and no broker can stop you position just if you have no enough money but you get a message before the broker close your position it's call margin and if you add money to your account you can keep it more time.