yeah as desik said, with time the shape of the pads will tend to change(because the foam won't get back to it's original shape indefinitely, or if it's not leather, the surface might become dirty or worn out). in effect, the driver comes closer to the ear as time passes, the inside volume and shape could change, the quality of the seal may change too... so the signature can change. I don't think anybody is challenging that old pads vs new pads usually don't sound the same.
so if you have little time to test the headphone, I suggested to keep the headphone placed over books or whatever to keep some pressure on the pads and badly pretend like it had been used longer. but I don't know how effective or significant this could be, after all I'd expect at least new foam to behave very well for some time.
about pink noise, audacity. generate -> noise -> pink... and you create the file you need.
Thanks for that!