Keep in mind this is not a Tozando product. It's a Mitsuboshi product that is sold through the Tozando site. I have not owned a Mitsuboshi Hakama, but I'm about to retire a Mitsuboshi keikogi that I bought in 2006. It's been pretty good, and I think 10 years is a reasonable lifespan. I also own a tetron hakama made by a different manufacturer, and I can vouch that the material is light and durable and holds the pleats well. I have a cotton hakama for special occasions, but the tetron one is my every day hakama.
As for washing with the koshi-ita, I'd be very hesitant to do anything that might damage it. I hand wash and drip dry my hakama in order to protect the koshi-ita. I got lazy and got a dry cleaner in Tokyo to clean it once, and they made a total mess of it. Soon afterwards the koshi-ita split. I think they totally ignored my instructions about protecting the koshi-ita.
That's unusual that the dry cleaners here would not know how to clean a hakama. My local one has been fine. I can even ask for the pleats to be ironed (Literally "pleats") and it comes back in perfect condition. That being said, the koshiita insert in my old cotton hakama fell apart not too long ago and that had been to the dry cleaner a few times over the years.
The Mitsuboshi products seem to be pretty popular here. Seido, as far as I know, sell pretty much the same Tozando and Mitsuboshi hakamas under their own name. If you train a LOT you might want to look into any options for re-inforcing the weak points. Other than that, usually the stitching comes undone in places eventually. The koshiita usually contains rubber.
One thing that is a bit odd is that if I followed their height guide, I'd be wearing a 26.5 (I'm about 173cm tall). I wear a 26 and I think it's too long. If I bought another one I'd get it a size or two smaller.