The most common causes of death in dialysis patients is not the kidney failure itself but actually cardiac arrest or arrhythmias.
Usually cardiac rest is the most common cause of a person dying when on dialysis.
However there have been many people on dialysis who have lived well for 15 to 20 to 25 and even sometimes 30 years while on dialysis.
Your age and other health are also a factor when it comes to the lifespan of the person on dialysis as the older the person is the less they'll live anyway due to their natural lifespan.
Being older makes it harder to be on dialysis even though you still can live well on dialysis even at an older age.
Some really old people opt out of having dialysis because they're likely to die of older age anyway.