Sure, the rain sensor might have near zero failures. I would think the rain sensor probably has failure rates on the order of bluetooth radio failure rates, but I had one of those fail. But what has truly 0 failures is to eliminate the rain sensor entirely. More importantly though, the rain sensor is just one of many, many toys the Audi had. Failure rates are multiplicative, so if you can remove 50% of your parts, you eliminate a lot of points of failure, plus a ton of extra wiring and electrical problems, plus the whole problem of integration.