As one might expect from steel rope core strings, these are very quick to respond, and have a resonant tone, and a nice ring.
Don't know yet how long they will last, but I certainly haven't noticed any change after some 50 or so hours of playing, which is already indicating that they'll last longer than the Evah Pirazzi Golds I had before them.
However, coming from said Evahs, I'm not overly impressed with the playability, overall tone, or dynamic range of the Helicores. They demand more from your bowing technique, but deliver less power and expression. (Fortunately, my new JonPaul helps a bit with that!) In particular, the A string is a bit temperamental on my violin; a bit prone to slip into harmonics. The Helicores will not take kindly to "digging in" the way I could with the Evahs, though they can still play pretty loud with more sophisticated bowing technique.