I think a tinnitus of stable loudness would be easier to habituate to. When it varies it does have a tendency to grab your attention which is the opposite of habituation. And, at some level of loudness, it is likely to be difficult to tune out. I've had tinnitus for decades. It always reacts to noise by getting louder but doesn't follow noise levels minute by minute. More of a delayed reaction, and once elevated, takes quite some time to return to typical levels, like hours, days and sometimes never. In spite of that, I do cope with it quite well, so I know it is possible. In a noisy office environment, I might not notice it unless I focus on it. In a quieter environment it is front, center and loud. But, I can still focus, concentrate and carry on. Perhaps this is because when my tinnitus started it was accompanied by pronounced hyperacusis. Almost all sounds were uncomfortably loud and that is what grabbed my attention. You might say the hyperacusis caused me to rapidly habituate to the tinnitus. Still, I wish it would just go away. But it is the hyperacusis I continue to struggle with and that really impacts my life.
So, a bit of a ramble, but indeed you can habituate to a lot, but a continuously variable tinnitus will be more difficult. I suggest working with an audiologist that has a lot of experience with tinnitus, and not one that just recommends maskers. Though some people have found maskers to be helpful, that will not help to get to the point where the sound just doesn't bother you which should be your goal. If you get to that point, then it is possible that the tinnitus could decrease in volume over time, as long as you avoid questionable noise exposures.