Kind of strange to do a blog post on back scratching, but if you lived in this house, it wouldn't be so odd to you. I live in a house full of people who like nothing better than to have their backs scratched. This goes for father and daughters. I regularly have requests to "scratch" which really just means aimlessly meandering over their backs with some slight pressure from my finger nails. They would probably sit for hours (if I was that obliging) and have their backs scratched. I've never had any of them say, "ok, that's enough." It usually ends with me "smoothing" it out and them saying "no, just a little more." Or in Emma's case pushing herself down into my arms again. When you think about it, back scratching really is a good thing to enjoy and useful for me.
If I need to calm any of them down all I need to do is scratch.
If you want to just sit and have some quality time, just scratch.
If they're having a bad day, just scratch.
If they're having a good day, just scratch.
If you want a long, melt-in-your-arms hug, just scratch.
This basically sums it up.