Your reply is interesting, smoothie.
My experience is simply that as time goes on, the nap of the sole becomes more and more difficult to restore, and i'm more likely to lose grip. Eventually, i treasure my feet and lower limbs enough to cough up the €20 (about $20) it costs me to replace them, and the difference is well worth it.
Recently, we started practising in a new hall, and for weeks i was complaining about the slippery floor. Then i changed the soles and heels, and since that moment, i've had no problems.
Maybe you have better materials in the US.