Water damage and a power boost
My I/O board sustained water damage while living in humid environments for the past 4 years, and it had signs of corrosion. The most annoying problem was the intermittent charging. The battery was not in the worst shape (~1200 charge cycles), but since I was opening up the case, I decided to replace it at the same time.
The guide was spot on. No issues at all.
If you have a compressed air canister, it is a good time to clean the dust that accumulates over the years. Take extra care when dealing with the small connections.
T5 Torx Screwdriver
P5 Pentalobe Screwdriver Retina MacBook Pro and Air
MacBook Air 13" (Late 2010) I/O Board
MacBook Air 13" (Late 2010-2017) Replacement Battery