I had a VW Touran for 4 years with the Autoglym treatment. Polished it once, just before I sold it. The paint felt just as smooth on the day before I polished it as it had on Day 1 of ownership.
My current Jazz has the Williams F1 treatment from new. 5.5 years on, I've polished it once (this year). Last year, at the four year anniversary, I clay-barred the car. Hardly anything came off onto the clay, so I didn't bother polishing it. It seemed fine as it was.
I realise some people will come up with scientific and other reasons why it doesn't work, but in my case, it appears to have worked as advertised. All I do is wash the car (and not with the two or three bucket methods, either) and dry it with Meguiars towels. Then I put the kettle on and don't stress about it!