Hmm, a few of those sorts of things have happened although he didn't seem upset at the time. One time at bedtime he asked me about time (I guess) - "So, are there just going to be days and days and days forever?" and we explained that eventually he'd die but it'd be a lot of days so now he says there will be "days and days and days until we die". He didn't seem upset but I guess that's kind of a heavy concept.

Preschool has also ended recently and he was a little sad about it. Both of those events were about a month ago but maybe it's taking a while for things to 'sink in' or something. Usually he rolls with changes like that but maybe he's feeling a bit more sensitive to it.