From my case, I use 1 mini and 1 Avent at the same time, normally finish within 20 min. I'll use them both in the beginning and if the letdown doesn't come quick enough, i'll use only the electric pump with another hand to simulate my other nipple. I found it's quicker than using Avent in the same way.
If i'm at home, i found that it's faster if i'm in a relax mode, like reading books / listen to radio.
My younger son (1yr3months) is still having my feeds and i am still pumping in the office.