Pump letdown/time

jkjohnsonwedding

Apparently some pumps have a letdown setting but I use the Ameda Purely Yours Ultra pump which doesn't. Is there a way I can force a letdown using the suction and speed settings? Everytime I pump, I have to pump at least 30 minutes to get "empty" and that seems like a lot compared to others. By the 10-15 minute mark I've only produced around 2 oz., but if I pump for 30 minutes I can get about 5 oz. During the peak hours (1-5am) I can get 9-10oz in 45 mins. I've been EPing for the last 4 weeks so I need to make enough milk in each session and I wouldn't if I stopped at 15 mins. =/ I'm debating renting a hospital grade pump to see if I'd produce more in a shorter time span.