Normally, the suspension will fail before total wear of the diamond tip. The suspension hardens with age and induces all sorts of negative effects: distortion, bass-lacking sound and the needle itself might fall off.
I have only encountered one of five original MMCx cartridges that still work. When (not if) the cart fails, you have the option of re-tipping at Axel Schürholz (http://www.schallplattennadeln.de/). He offers great quality replacements and most Beogram users in here have positive experiences with him, including myself. Service is great and your cart will be good for another 20 years
Beocenter 9300, Beogam CD50, Beocord 5500, Beomaster 3400, Beomaster 4400, 2 Beogram 4000, Beomaster 8000, 2 beogram 8002, Beovox S-75, Beovox MS150.2, Beovox RL6000, Beovox S-35, Beomaster 6000, 2 Beocord 9000, Beocord 8004, Beocord 5000, Form 1, 2x Beolink 1000, Beo4, MX3500, LS4500. Born 1993.