limits of improvement & happiness together?

I'm new to this forum and have posted a couple of times.  My partner has ADHD (as well as other disorders). We've only been together 3.5 years. 


A friend told me that she regrets that she stayed with her husband.  She expressed concern for me (I think she was indirectly telling me I should leave my relationship and learn from her lessons).  I feel sad reading the posts that say while ADHD relationships can improve, they never become equitable.  And I feel sad seeing people stuck after decades together, afraid to leave or at great costs.  I'm not judging anybody's choices or experiences, just expressing my authentic emotional reaction of heartache.  I guess ultimately, many of the stories cause me to feel doomed in the long-run if I stay with my partner.

Financially, without me, I believe that later in life she will likely end up living on the streets (unless someone else decides to parent her).  I'm not interested in supporting (or probably more accurately 'enabling') her the rest of my life.  I'm relatively young and don't have kids, so it's a lot easier to get out at this point.  I haven't chosen to leave, but this forum is causing me to question if it's worth staying for in the long-term or how.  The stories from all of you who have more experience are shaking me up.