Good find, I remember this!
Quite possible they went through a bad spell, I mean it doesn't really matter when you get married or to whom, ups and downs are bound to happen.
Camilla is an extremely messy person, she used to drive her roommates up the wall with this back in the day before she married APB.
Keeping separate houses like this isn't unusual, those who don't do that in their circles have instead separate quarters. Like normal people sleeping separately because of the snoring problem, just bigger
These days, they are too affectionate with each other and Camilla has for instance real trouble in hot climates, it affects her health and she still goes on tour with Charles regardless. If the marriage were *ahem* "irretrievably broken down" (sorry, couldn't resist
) she wouldn't tour with him places that literally knock her off her feet, esp at her age. She does also arrive earlier than Charles sometimes to acclimatize and prep stuff for him (!!), but also leaves earlier. No spouses who regret marrying each other would do this and then be warm towards each other on top of that.