I bought these over two years ago with pair of Superlux HD-330s, and they've seen almost daily use since then.
These are very comfortable and soft. I just got pair or Superlux's pads to compare, and these are softer & more comfortable to wear long periods of time.
After two years of almost daily use the pads have held well. They have molded to shape of my head and have flattened out a quite bit.
Haven't noticed that these would have really affected the sound quality. Compared to new pads the sound quality feels maybe tiny bit worse, but my pads are quite worn out.
tl:dr: Great pads. Well worth the money.