Not all organs would be able to replaced, so you're there's a few ways to die
As you age and pick up more health issues, the risk of postoperative complications gets greater, and you might die from one of these surgeries or as a later complication of the organ transplant. At some point, the risk of death from the surgery would be higher than the benefit from survival, so if you chose to transplant, you might die faster.
You're on a relatively strong cocktail of immunosuppressants and with every potential insult to your body, these could be too strong in some way and need to be reduced which increases the potential for the body to start developing a response against your organs, or you might pick up infectious diseases that only affect immunosuppressed people which can be hard to treat