I guess I would have to look at both the garment (how it is made and how it is worn) and the fiber.
The fewer times that a garment would need to be laundered, the longer its longevity. Also, classic patterns that can be worn in any generation helps.
I have a wool jacket that a great-aunt knitted when she was a teen in Germany. It must be 80+ years old. She lined the jacket and I don't think she ever "washed" it, per se. I replaced the lining and had it dry cleaned once. I still get compliments on the jacket when I wear it.
I also have wool sweaters that my Nana knit for me 26 years ago that my daughter is wearing now.
So, my personal history points to wool being a good call. The sweaters that I have knitted for my dad and DH have held up really well and they are out of a wool/rayon blend.