After updating my MacBook Air to 10.8.5, I read some interesting stuff on MacWorld about the update. Turns out it included the MacBook Air Software Update 1.0 – which was released on 18 July but was only available for Mid-2013 MBAs. This update included a fix for “an issue that in rare instances may cause an intermittent loss in wireless connectivity”. And that of course is the issue I had on my Mid 2012 MBA. Better late than never, I guess.
It explains why my WiFi has been robust since the update, anyway.