The T-adapter? That’s not mechanically complex and should literally last forever if made out of the correct materials and isn’t touched all the time. It should be no more fault prone than the connection to the toilet.

A misaligned thread or a washer not fitting quite right might be an issue from a bad install. That’s an easy fix though and you should see a leak before things go catastrophic.

If your really looking for piece of mind I’m sure there are t adapters that can close themselves down in certain failure states.