Burning in the M80 is not going to alter the bass much if any. I suggest a new headphone if you are like me and cannot stand the low end on the M80. I often recommend them, but always include the caveat about the bass.
If you like the fit and other aspects of the sound signature of the M80 the Sennheiser HD-25-1-ii is what I recommend. They are very well built and have a similar up-front and even sound signature like the M80, but the bass is much more in control.
Here are some charts for the M80 and HD-25-1-ii:
To me the only evidence that I can see of the bass issue with the M80 is a slight upward peak at 210 Hz, but I suspect the issue has more to do with distortion Perhaps Tyll Hertens will chime in and help explain why the bass seems so emphasized on the M80 compared to the HD-25... when the charts show a drastic similarity.
To my ears the HE-25-1-ii does not have the hurt your ears bass that the M80 presents.