Hey Pete,
what you describe sounds like a harmonious relationship, many people would be envious about.
Not replying directly to your questions just a quick sharing... my partner/fiancee has waist long hair. Since quite early in our relationship, I "came out" in the sense that I shared (over some time) pretty openly that hair plays a very important role in my erotic life and that even though I'd love her even as bald, I totally enjoy her long hair and would very deeply regret if she cut it. I also made sure she understood that in my case, this goes a bit beyond "i just like long hair", she knows long hair drives me crazy
We both do things to make the relationship better and so she made her long hair a part of it.. we do all kinds of things with it........and yes I also am getting her the very best (and most expensive ;)) natural hair products and treatments you can imagine... she seem to be enjoying it, although she'd probably cut the hair was she single.
I think open communication among partners is the key, really, not just when it comes to long hair
All the best
K.