I revived my AT440ml cartridge I had kept unused for over 20 years. Had no more than 20 hrs on it.
I thought the rubber would be hard, but after I thoroughly cleaned the whole tip/cantilever/rubber suspension and let it break itself in playing a few unimportant LPs.
It sounds surprisingly good. compared to my shure V15Vxmr body/Jico Stylus SAS/boron/brush, it competes with it same as when new back in late 90's.
Next, I put a drop of rubber renew on the suspension that I use for Reel to Reel capstan wheels, belts ...