I have an ongoing battle with trash cans. When does one make the decision to pull the bag? One must let there be enough trash in the can to make it worthwhile to take it out, so as not to be wasteful. On the other hand, one must not let the can get too full or too heavy, making pulling it out difficult, or creating the dreaded spillage.
And there is always much more room in the bag than the receptacle lets on. Once I pull the bag, there's almost always room for more once it is out.
In garbage, as in life, timing is everything.