@Ed209 - Thank you so much for coming back with such an informative reply.
My noise ramped up in June 2014, after a particular musician (a friend of 35 years) decided to play far too loud, and far too close.
Since then my hiss/noise level has been constant.
However, I was really interested in your case because I have become aware of a similar pattern in my own experience.
Having been in hell for three years, I am realising days when I am living well, conversing well, feeling benevelant to all I meet, and enjoying life.
I no longer look for a cure, far less expect one.
As a Tinnitus owner (I dislike admitting to sufferer) I am beginning to live well almost alongside it.
A different plane, as you say.
'Habituation' seemed like a too 'high-falutin' description, but just maybe I'm getting there.
I have Tinnitus - I expect some hiss - more often than not, I don't care.
I am very grateful for your time Ed.
Thank you
Jazzer