Android MapView Overlay refresh timing

Question

I need an overlay that refreshes with 2Hz - for animated Overlays. There is this second draw() method which triggers a redraw when you return true.

public boolean draw(android.graphics.Canvas canvas,
                    MapView mapView,
                    boolean shadow,
                    long when) {

This is all working fine, but I need to slow it down that it does not consume that much CPU and battery. - I think the key is this long when parameter, but I have problems understanding how to use it (as I get it as a parameter and I see no way to set it). The documentation is not really helping there either.