With some pieces I have heard little to no changes even after months of listening and other times I wondered if my gear was doing the whole William Hurt/Altered States metamorphosis because the changes in sonic character were so fickin' wild and extreme.
Therefore, I'd say it depends on the exact piece of equipment whether break-in will be noticeable, and also on the sensitivity one has to perceiving it.
Therefore, I'd say it depends on the exact piece of equipment whether break-in will be noticeable, and also on the sensitivity one has to perceiving it.