I usually focus on two, maximum three currency pairs at a time, though the exact currency pairs occasionally change. I don't watch less because some of them aren't suitable, at least to me, to trade at all times, and I don't watch more because I would miss things if I were to watch too many pairs at the same time.
I only trade multi-day and through orders placed after the London close. This means I can view the charts of multiple pairs and always find an opportunity each evening, though I stick with the major pairs as the £ per pip cost to the stop-loss is then affordable. Many long-term trends in forex have evaporated in recent months so recently I find sometimes I am in a longer term (5-15 days?) position in a pair but also taking a shorter term (2-4 days?) trade in the same pair in the opposite direction as price bounces around.
Once the trade is open, I use orders to exit so I'm not tied to the screen.
i cover 26 pairs, at any one time through out the week. i can have anywhere from 1 to 26 orders open
You can have 26 open orders!?
How do you account for overlapping positions and their implications for your total risk? For example, if you get simultaneous signals to go long EUR/USD and short USD/JPY, you ended up double short USD. Or if you were long EUR/USD and long USD/JPY you'd effectively be long EUR/JPY with perhaps a small residual USD exposure left over.