With a new restart, and not having seen Lydia skulking in my bedroom for ages in previous playthroughs, I had forgoten about her initial 'interest' in watching people sleep.

This new run-through, I've been soloing with the Dawnguard quests, after having adopted Lucia as soon as I got Breezehome, and I've left Lydia there to do the house-mother thing.

Well, I just strolled into the house, did a bit of stuff, then wondered where everyone was...off I stroll, no, no Lydia in her room...no Lydia in my room. Yup...there's Lucia racked out catching z's, and there's good old Lydia sitting on the end of her bed munching on a loaf of bread....

Some things never change...