At 10-12 months old, when Rowan was starting to take shaky first steps (walking full-time by his birthday), he went back and forth on 1-2 naps. He was getting more tired as he used more energy during the day being so active (while calm and placid in his personality, physically he is a very active child). Once walking got easier he stayed at the one nap per day - and it has been a decent-length one: 2-3 hours most days.
With the other nap-dropping, there was warning because previous naps got longer or the second/third sleep got shorter, but it's different this time. There's toddler defiance (wall kicking/banging; so I'm unsure whether it's stubbornness or what), and more consistent night sleep. Our pre-nap routines are the same so I'm not sure what it happening here.
Time will tell, I suppose. I just wanted to make a note of it in here so I can look back in later weeks/months in case there's a "a-ha!" moment somewhere. ;)
For the time being, I shall lament the loss of the daytime nap/tea break!!