It seems to vary widely person by person.
There's a guy I follow on Reddit, he has a blog that he keeps religiously, he's been in remission over 20 years.
There is also a T2 couple I corresponded with that have 45 years remission between them, great support structures.
In both cases it's been maintained weight loss & low carb diets that they attributed to their remission longevity.
Indeed the husband of the couple told me that a Junior Doctor told him about low carb the day he was diagnosed but asked never to be quoted on it for fear of his medical licence.
As far as hard data on remission goes there are long term studies such as the Swedish Obese Subjecys Study, ran for 20+ years.
As you can see bariatric surgery weight loss results varied based on the procedure.
There was large scale remission of T2 in the first few years, this decayed about 50% over 10 years as shown.
Now remember this data goes back years, long before low carb was even a thing.
I do remember seeing that the greatest factor for remission was duration of T2 before surgery & whether or not you'd already progressed to insulin.
Anyway, remission doesn't sell meds so pharma are not interested.