Definitely the Achilles heel in any C64 setup. Perhaps new PSUs are visually distinct from the old ones, but practically everyone had to replace theirs as they aged.
Now the 64C was released in 1986, four years after the 64 and its faulty power supplies came out. I don't know whether Commodore had decisively fixed the flawed PSUs by that time, but I know for sure that my second PSU lasted for the lifetime of that device too.
