I spend nearly 30-45 mins. Because I try to pump out as much as I can (usually 15-16 oz per day), I will use medela electric and avent at the same time first. Then I use my hand to squeeze it out. Sometimes, I can get 1-1.5 oz more when I got reflex. I learn how to pump milk by hand from bk.
I use 2 pumps at the same time in the office so as to save time. It takes me about 15 mins to pump about 6 oz from both sides. If time allows I think I can pump more.
I did feel a bit painful when I first tried pumping but now I don't feel much... maybe I've got used to it...