Some instructions I see for refilling these say to suck all the air out of the chimney after filling. Is this really necessary since the carts sit in the printer in such a way that the air rises anyway? I understand you wouldn't want like half the chimney full of air, but having a few little ones doesn't seem to be a big deal to me. We don't sell too many bag style carts, but I am curious as to what other people think about this.