As much attention as antique cars get from their owners, leaks are likely going to be found long before a failure.
As a counterpoint, I suffered a catastrophic brake failure on my buick and narrowly avoided an accident because it had a dual MC and the rear brakes still worked.
There were no leaks, but one of the braided softlines blew out of its crimped end during a hard stop and I lost the front brakes.
I am a big proponent of modern braking safety equipment.