Hi old_john.
Re: Using GTC orders.
I have every one of my next Sells in as a GTC (plus extended hours when available), good for 4 or 5 months.
I rarely use GTC's on the Buy side.
But I set Alerts for for both prices and as soon as it gets there, I get a text.
If it's at my Buy price, I take a look and decide.
If I go for it, It might be a GTC at or a little lower if that seems to be the trend, or if it's 'waffeling' around my price, I'll execute as market. Typically not more than a few pennies difference.
Been doing this for years at TD-Ameritrade.
Works well for me.
Best Regards, Steve (The Grabber)