Long time hold positions are bad in trading systems, because your margins will not be free until you hold positions and new trades will not take positions. So you do not have to trade for a long time, a maximum of a day is the maximum time to hold your position and you should clear all your positions on the same day of trading. and Of course there is no limit to your open trade but only one condition you must have sufficient capital in your account to hold your open trade. But there are no other conditions. The best option opens a swap-free account where there is no cost to open a trade for a long time!