With Xander, I pumped every 3 hours and would pump for 20-25 minutes. I recently met with a LC who said you should only really pump for 10 minutes, 15 minutes at the most! I always seemed to get a second letdown around 20 minutes into pumping, but I have no idea if I actually got that much from that second letdown, so maybe it wasn't even worth it.
How often did/do you pump at work? And for how long?