Dear Ima shel Alon, thank you so much for your detailed response! You're a lifesaver.
Will implement the gradual lengthening of his A times. I tried that today, with the result that he very quickly got overtired and slept only 1 hour for his afternoon nap. Is that to be expected?
What's happening for the last 3 days is, when we try and put him down for his 3rd (sometimes, but rarely nowadays, 4th) nap at around 5 PM, he just doesn't go down. Cries, flops around the cot. We leave him to try and self-settle, he doesn't. We shush-pat him, he just cries even more. As a result, he stays awake right until 7-7.30 PM, by which time he's completely hyper (he's been up since 3 PM). Then he goes to sleep.
Why do you suppose this is happening? Is it related to the shortening of his 1st/2nd naps? Is all of this because of teething, d'you think? Or because of any 6-month sleep regression/transition thingy?
Just that we worked really hard with the PUPD/shush-pat to establish good sleeping habits and nap routines, but now it's all disrupted, don't want to get into accidental parenting and undo all the good work, if it's just a phase!
What should we do, specifically, if he's going to resist the 3rd nap so vigorously? Should we drop the nap and give him A time, should we insist on him napping and continue to do s-p/PUPD? What we're doing right now, is taking him for a drive and see if he naps in the car.
Thanks once again!