How many coffees can I make before the empty ground container light on my TrueBrew goes on indicating I need to empty the container?

it is not a fix number, it depends on the different recipes that you make. The machine calculates automatically how much powder has been used for the selected beverages showing the allarm light accordingly. If the grounds container and disposal water container have not been emptied in the last 72 hours, the machine will indicate you need to empty it even if it is not full. You should always keep both containers clean and not wait for the warning light.