Not got time to read the whole thread...
But just wanted to reassure you GoTheFkToSleep that you're not the only one out there! We do worse than that in our family, and, do you know what, it's amazing how humans don't actually keel over and die because of lack of washing!
My daughter just turned 7, at 6 she was generally reluctant to bath and have her hair washed. To start with I would decide we should do it once a week, but never decided on a day, so after a while I decided it should be at least once a month. I woke up one day, realised it had been 3 months since any washing at all. I looked (and smelled!) her over closely, and concluded there was nothing wrong with her that I could spot. Her hair tends to look like it might need a wash, if not today then tommorrow - but it never gets any worse, it just stays like that. Occasionally she'll have a foot wash, but I've been surprised how long she can go without her feet smelling at all. She does go swimming regularly, and refuses to go in the shower afterwards. I suspect that with none of the natural hair oils being washed off, the chlorine is likely to bounce off.
Having seen the lack of effect (I'd be surprised if anyone actually noticed without being told) I am now perfectly happy for this state of affairs to go on indefinately (it's been more than a year now). There are people who give up washing their hair - just google "no poo" for example, some of them don't wash hair at all as adults.
And when I think of all the time, energy, money, water, plastic bottles, chemicals and pollutants I'm saving, I feel I can put up with other people's shock and horror perfectly happily - as long as my daughter is happy also.