I have been applying it weekly. To be honest, to keep it looking like that picture you need to do it weekly from my experience. Especially with all the rain that has been around. The dash however was applied 2 weeks ago and I wouldn't do it any more than monthly.
We have a new product on the way from the US though that is a permanent solution called
Forever Black. Nero can be applied over the top of forever black to give it that slight wet look, but when the Nero wears off your tyres will still be black rather than that grey colour they go.
Nero is $25.65 with the forum discount for 16oz (473ml)