Hey
@Stacken77 mate,
Fortunately, I have to date, not experienced any noise exposure that has reset my hyperacusis to it's original severity, or chipped away at the improvement I've made.
My severe hyperacusis began a day or two after the onset of my severe tinnitus.
I remember three days after lying in bed not sleeping and having to stay up watching strange Chinese films, I had finally used up all the resources in my apartment and had to go shopping.
I had never heard of hyperacusis in my life, and as I was walking down my street to the shop that morning, an aeroplane flew over. The noise was like nothing I had ever heard before. I almost died. That was it, my introduction to the nightmare that was hyperacusis. Everything I had ever known, turned up in volume x10.
So yes, I lived with it at this awful baseline level for many years, and then it started to improve, as you say.
I had, as you know, began wearing ear muffs at home, and this was giving me frequent ear infections and I guess, maintaining the hyperacusis at it's then severe level.
It was the advice on support forums I kept reading, and then my Mum, who kept encouraging me to try not wearing the ear muffs that convinced me to finally try day to day living, without resorting to them for comfort.
I also, as you know, have had a couple of permanent spikes in my tinnitus since the onset in 2009, but none of them ever affected my hyperacusis, by some stroke of luck; just gave me a new and worse level of tinnitus I had to habituate to.
TL;DR: My hyperacusis has never gotten worse since the onset of my severe tinnitus and hyperacusis in 2009, and has only improved since I stopped using hearing protection at home, around 2013-2014.