I've been exclusively expressing for 8 weeks and it is incredibly hard. For the first 6 weeks most need to pump 8-10 times a day, after that about 6-7.
I have to pump 9 times a day, 20 minutes each boob. Thats 6 hours a day pumping.
It is hard when you re pumping and the baby cries, and you have to figure out what to do.
It is very stressful, I wouldn't recommend it as a choice.