replaced a Macbook Air battery in 20 mins, saved $50
10 - 30 minutes
My battery was failing,
I got the kit from ifixit, it arrived in 1 day, and it took me 20 mins to reaplace the battery
Definitely do it yourself for this repair.
MacBook Air 11" (Mid 2011/Mid 2012) Battery
T5 Torx Screwdriver
P5 Pentalobe Screwdriver Retina MacBook Pro and Air