For me the failure mode is the naps becoming too long. Taking naps too late makes it impossible to sleep in time for me, too.
You need to have an alarm clock or sleep tracks that will mechanically wake you up after 20 minutes. You go to deep sleep if you sleep over 30 minutes, and then you start getting sleep inertia and messing up your night's sleep.
This is the public group instrumental rationality diary for November 16-30 (that I've now fished out of my drafts folder, *cough*.)
The poll earlier this month seems to be sufficiently in favor of maintaining the current schedule that extra votes are unlikely to change things much, but if you'd really like to register your opinion, you are welcome to do so here.
Thanks to cata for starting the Group Rationality Diary posts, and to commenters for participating.
Immediate past diary: November 1-15
Rationality diaries archive