My LC (an IBCLC) recommends pumping after each nursing session starting 2 weeks before the return to work - she believes that this stimulates supply most effectively and will allow for the accumulation of enough freezer stash that mom can settle into the routine of being back at work.

I am not a good example; my pumping after nursing only 2-3 times per day stimulated an oversupply. I had to stop pumping for several weeks at the end of my maternity leave to correct it. There is NO way that I could have pumped after every nursing session - things would have been even worse.