I do love mine and I use it for a shower every day and it looks brand new after 1 year plus. Use the search box here for the words Archer tub and I think you'll find lots of compliments for that one by Kohler.
When I had confusion with Swanstone I called the PR department phone number (or maybe emailed?) from their website and got great information about their materials. Try Kohler company headquarters to ask your question about acrylic grades.
Here is a forum thread linked about the Archer tub.

Here is a link that might be useful: discussion on Kohler tub

We have the Kohler Devonshire acrylic tub, and really like it. Quality seems very good. It's nice and deep, too.

Thanks. The plumbing store said more specifically they find they start to yellow after 10+ years.

In a decade i will probably want to remodel my bathroom again anyway! lol.

I will call Kohler and ask if the ones sold to big box stores like Home depot are the same as the high end stores.

I absolutely love my Kohler Expanse. My neighbor has a Bancroft and the Expanse seems sturdier. It's also much larger.

i wish we could fit the expanse in our space! it is just too wide.

Glad you like your tub!