HAHA So you should be able to use your headphone at their full potential after over 3 months of burning them in? You can't leave the headphones on any noise for long periods of time like that, not even a day at a time really. I personally wouldn't expect any kind of sound changes over 40 hours.
Er, yeah... I was being sarcastic. Just to be clear, I don't believe in burn-in at all.