Well the actual driver inside should last you a lifetime, the plasticky headband on the other hand...

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Also related:

The Sennheisers branded ear pads or Brainwavz (IIRC) ear pads are a bit expensive ($20+).

You can get generic "memory" foam ones on AliExpress for $4.

It's not actually memory foam and they might send you the wrong type, and it's a tight fit (just remember to breathe !?) but they work.