Adding an SSDT didn't solve the problem. Started testing last night: system made it through a number of shorter sleep cycles; left it to sleep overnight, system made it through without crashing, waking by itself approximately every two hours (despite darkwakes set to 0); let it go back to sleep for another 1.5 hours, at which point it crashed at the password screen upon waking the system from the keyboard.
Before it crashed I noticed a graphical glitch in the rendering of the blurred background image at the password screen -- since I'm using integrated graphics, this suggests memory corruption to me. Checking the system log, I see a cascade of errors, starting with the Finder and then the Window Server crashing; logging ends two seconds after wake, and the system reboots itself thereafter.
A few other notes on adding an SSDT…
Here's sample output from pmset -g live without an SSDT:
Code:
$pmset -g live
Active Profiles:
AC Power -1*
Currently in use:
hibernatemode 0
womp 0
networkoversleep 0
sleep 3
Sleep On Power Button 1
ttyskeepawake 1
hibernatefile /var/vm/sleepimage
disksleep 10
displaysleep 2
And here's the output with SSDT:
Code:
$pmset -g live
Active Profiles:
AC Power -1*
Currently in use:
standby 0
Sleep On Power Button 1
womp 0
hibernatefile /var/vm/sleepimage
darkwakes 0
networkoversleep 0
disksleep 10
sleep 3
autopoweroffdelay 14400
hibernatemode 0
autopoweroff 0
ttyskeepawake 1
displaysleep 2
standbydelay 10800
Here's the Energy Saver pref pane without SSDT:
And here it is with the SSDT:
Notice that with the SSDT 'Computer Sleep' control is absent and 'Power Nap' toggle has appeared. Even though 'Computer Sleep' isn't in the pref pane, it can be controlled using pmset from the command line and the appears to work as expected.
Also, I noticed that adding an SSDT makes the 'Remote Disc' item appear under 'Devices' in the Finder sidebar.
I'm not sure which avenue to pursue next for testing.