Mostly, you need to make sure you express the same amount your LO eats. Preferably close to the time they take the bottle, but it doesn't HAVE to be that way.
When I express at work, I do 2x per day. By the end of the day I usually end up with about 16-18 ounces. While I am away LO has either 2 or 3 bottles of EBM (which means he might get one more feed than I pump), but only eats about 12-15 ounces for those feeds. That means I am always pumping just a bit more than he is eating. It is working for me.
So, if you can just make sure you pump at least as much as LO eats every day, your supply should keep up with him. I wouldn't make a habit of going without pumping when he eats, but once in a while should be okay.