El Capitan crashing
It took a while, but I think I fixed my El Capitan crashing problem. Too much old mail? Details on my post on discussions.apple.com.
Update 17 Dec 2015: Nope, still not fixed :-(((
Update 21 May 2016: Since resetting all my power management settings, this seems to be fixed. System Preferences > Energy Saver > Restore Defaults
Update April 2018: Well, the disk finally failed, so that fixed that problem…