So as I've mentioned in passing, our kids don't tend to change their clothes in any periodic fashion. That is, they tend to wear the same outfit as long as they're still feeling it (or it gets wet or uncomfortably dirty). Not to say that they always stay in the same clothes for long periods of time—sometimes activities call for several changes in one day. But they don't ever feel like it's necessary to put on something different just because it's a new day, still less because they're going to bed. So pajamas aren't a regular feature of our bedtime routine.
But! On the other hand, it's undeniable that pajamas are awesome, especially when they're new. And this fall all three boys have got at least one new pj outfit each, so at times there's been considerable excitement around them. Tuesday and Wednesday not one of them changed out of pajamas at any point—the same pjs over the two days. Sure, Tuesday was a wet inside sort of day, but Wednesday they were at Grandma and Grandpa's all day, and went for a walk. In their pajamas. Only a trip to the dentist this morning, for all three of them, forced a change. Now they're all in bed in the clothes they wore all day.
I don't see anything wrong with any of that. Personally, I don't care to let my dirty work pants into the bed; but when I take them off to sleep I just put them back on the morning, most days, so I have no room to cast aspersions. But it is funny when, as happened the other day, they slept in their clothes and then changed into pajamas after breakfast. The game they were playing demanded it. It makes sense to them, so who am I to question?