I wondered if maybe the police officers surmised that it was once a year or so from circumstantial evidence - eg, "we were allowed to shower before photo sessions", and the police can see from computers and downloads that there were photo sessions once a year.
Don't know if this article/ information has been shared yet, claiming they had hopes of a reality TV show. If the situation wasn't so tragic, the idea that Louise thought she had a reality TV formula here is laughable. It shows that they were both delusional enough to dismiss their torture as an off-day, and when they had their reality show it would all be different, just like the next baby was going to be different, and the next wedding renewal was going to be the one where they really pulled their relationship together.
http://www.news.com.au/world/north-...w/news-story/b9db69f7820982e450d8b6fa71b97f0b
I see the disintegration happening from two or three pressure points: (1) they really couldn't manage and they were completely overwhelmed, trying to make the impossible stretch between their imagination and reality; (2) they were sadistic enough to punish the kids for being real growing children with needs - it takes a lot of evil to watch a person starve, let alone all your children; (3) the worse it got, the more frail the children became and the more messy the house became, there was more pressure on them trying to figure out how to manage the next step. So there's a downward spiral, with occasional highs where they dragged out the red t-shirts and blue jeans, mocked up a perfect family photo, told the sister airily that they don't know what money problems are, and then they start again from point one.