With strings this cheap it is OK to change them every month. It is nice to always have clean fresh strings on the guitar.
The tone is fine but the finish is not super smooth. I tried the strings on a slide guitar but had issues with the non-wound strings being noisy when moving the glass along the strings, it seems that the string surface is not perfectly smooth, even if this can't be felt by hand. However they feel comfortable to the fingers.
The overall impression is good and the price is fantastic.