I switched to exclusively pumping when DD was 2 and a 1/2 months old. She was becoming to distracted while BFing and breaking her latch to look around... which upset her because she in turn would expect the breast to follow her wherever she wanted to look. DD is also a slow gainer, and my midwife used to tell me I had to force DD to eat whenever she seemed hungry or slightly fussy... which I think in turned stressed me out... so at least with pumping I was/am able to monitor how much breast milk she is taking in.
I usually pump every 2 to 3 hours starting from 8AM each day and finishing at 11 or 12PM... So usually I have 6 to 7 pumping sessions during the day. Each session I will pump and drain both breasts. I don't pump over night... for the first few times I didn't I woke up very engorged, but I eventually regulated in that regard.
I use to have the Electric MiPump, and it broke after two uses. I have since switched to a manual Lansinoh pump and it works wonders for me. I find I can pump faster with my manual pump than I could with my manual pump.
If you have any other Q's or what not feel free to PM me.