Here's the update to my log, got another wifi drop some time overnight: wifi still dropping every 2-3 days. As stated before, I don't use bluetooth, iCloud, or Photos, and the same behavior has been happening with every Yosemite release since late October 2014 on my August 2012-purchased Macbook Air. I recently realized that it probably doesn't have anything to do with my August 2012-purchased Cisco/Linksys EA4500 5GHz router, since when wifi drops, I can't see any of the other 30+ routers in the vicinity:
04.09.2015 at 1:37am starting running and monitoring wifi after update to OS X Yosemite 10.10.3 (14D131)
04.11.2015 at 8:04pm, after having been out all day, arrive home to find that wifi has dropped.
04.12.2015 at 11:44am after shutting down, then turning on, wifi was back.
04.16.2015 at 6:22pm (thursday, after having been out of town) arrive back home to find that wifi has dropped.
04.17.2015 at 8:57pm booted into safe mode and wifi was back.
04.17.2015 at 8:59pm booted back into regular mode and wifi was still back.
04.19.2015 at 10:26am awoke to find wifi had dropped.
04.19.2015 at 10:28am shut down, turned on and wifi was back
04.22.2015 at 10:08am awoke to find wifi had dropped.
04.22.2015 at 10:11am "restart" didn't fix it but shut down did.