With a What did you buy and What did you listen to thread, I figured this would be a decent add on.
Maybe you reached a new milestone while training or you finally reorganized that junk draw and you think it looks nice.
For me today I replaced the pads on my HD6xx after using the originals for 5 years. Although they never became uncomfortable it was apparent they were well used and the velour soaked up its fair share of hair/skin oils. I love the velour but i wish it could be cleaned.
I spent the time to pop most of the headphone apart and clean out the accumulated dust and debris and random hairs. I suggest that at the very least people pop out the ear pad and clean between it and the plastic surrounds.
Here is a comparison of the old and new pads: