I read another thread where the poster said SI only lasted a couple of months.
I am sure the durability range for any LSP varies depending upon the weather, frequency of washing, exposure, type of shampoo used..etc.
My car sits outside 24/7. I wash with Optimum, or Finish Kare 1016. During the winter I use a waterless wash. Sonus has held up fine for 5 months, but keep in mind the products I have used to clean have some protection built in also--Optimum Wash n Wax, and Pinnacle waterless.
Ease of use was my favorite thing about Sonus Ion. It appeared to look like a polycharged version of Powerlock, same color, etc.
Overall it was worth the $$$, I have spent 75-100$ on a tub of 2 brands of wax before, and a application of this lasted a lot longer than those.