I don't think these types of earphones are worth replacing. The same $30 will get you some pretty nice headphones with a much better range of audio, clarity, and bass response.
Another reason to upgrade to a different type of headphone: People who wear the little white earbuds are at a higher risk of having their iPod taken away from them by force. Crooks know that white earbud = iPod (in most cases). Case in point: I was listening to my iPod with the white earbuds once and had someone who I walked past suddenly turn around behind me and try to grab my iPod out of my pocket. Luckily I pay close attention to my surroundings (even while listening to music 😉 ) and made a run for it (it was also lucky for me that he chose not to make a scene by chasing after me...). I realized afterwards that I was singled out because they knew I had my iPod just because of those $*#@ing earbuds. I immediately bought a pair of headphones, which I've been wearing with my iPod for over a year now, and no more attemped muggings (they probably think its a CD player or something).
I was happy to switch to a different type anyway, because if I wore the earbuds too long, they made my ears sore.
YMMV, though.
