depends on how you go about it- if you do it gradually, then you probably won't have much discomfort after your last session. If you do it suddenly, then it can take a while.
when i stopped last time, i did it gradually, eliminating pumps over time. Then i shortened the length of them. I finally stopped and had minimal discomfort for a day, then nothing for over a week. At 10 days or 2 weeks (forget exactly) i had the need to pump and felt full. one pumping got 5 ounces, and then i was dry there after.
if you feel uncomfortable, you can pump to relieve discomfort but no more or you'll stimulate production. Minimal pumping can help prevent clogged ducts or an infection. if possible, try to wean gradually- maybe drop a session every few days. this is more comfortable for you and if the baby is having trouble with formula it may help her system adjust. when you shower, face away from the shower and don't let the water hit your breasts. i have heard cold cabbage leaves can do wonders as well, although i don't have experience with this. wearing a tight sports bra can help speed the process as well.
by the way, if you are not engorged or uncomfortable, you shouldn't bother pumping and may be able to go cold turkey. some milk will be there for a while, but if it's not bothering you then don't worry about it.