How long does water take to flow into Lake Eyre in Australia?

Water rarely flows into Lake Eyre, one of the lowest points on Earth. It is usually a salt flat, filling only after heavy rains fall in its vast catchment area which covers parts of Queensland, the Northern Territory and South Australia. This can happen as infrequently as once every few years or even decades - in 1974 an extreme weather event filled the lake by mid-April which did not recede until late 1977; although that is an exceptional case.