So, I just passed the three week mark of my experiment with sleeping twice during the day - a shorter night followed by a long nap in the evening.
As my original goal was to try it out for two weeks, you may have already guessed that it works for me, and I have decided to prolong the experiment until two months instead.
Here are my insights so far:
I adjusted fairly quickly to taking a longer nap in the evening. That came as no surprise as I have been prone to napping before, but I have come to realize that the feeling of drowsiness that always used to accompany waking up from a late nap may have to do with the fact that I didn't have it as a routine, instead napping now and then during a month. When you take the effort of getting used to it, the process of waking up goes faster.
The same goes for falling asleep. Two weeks in, it became apparent that I was becoming addicted to my evening nap, to the extent of automatically starting to feel a bit sleepy and slow around six thirty to seven every evening. Now, I have never had too much difficulty falling asleep, but I am somewhat amazed by the fact that when I decide to take the nap, I usually don't have time to think more than "how am I ever getting to sleep, I'm not tired" before drifting off!
Someone asked me if I take the nap in my bedroom or on my couch. I tried both, and it does not seem to matter, so I just go with whatever feels more comfy at the time. I do set an alarm (I use the excellent PowerNap function of my Pebble) but I find that I consistently wake up before the alarm, just short of one hour into the nap. I know that you're supposed to try stretching the nap to 90 minutes but I have yet to be able to sleep that long, so I may have to come back on the topic.
After a late (in Swedish terms) dinner, I usually have a peak of energy ranging from around nine until bedtime, which is about midnight until half past twelve. I get up at 5:30 and while I would lie if I said that it is pleasant every morning, it's mindboggling to me that I'm able to both stay up fairly late and get up at freaking half past five! Winning the internal morning fight and getting up usually means that I am fully awake and on the go about halfway through my morning routine. Amazing, indeed!
I have to say that this seems to work for me. The adjustment period was just short of two weeks, until I stopped feeling jetlagged during the day, and now it feels like I've been doing this most of my life. Perhaps it suits me, as I have a natural "dip" in energy levels during the evening, and it just seems natural to take a nap instead of wasting time being tired. I recognize that this is not for everyone, but I will keep going for a while further, and keep you posted.