如何定期更改SKActions?

我想在生成几个矩形(SKShapeNodes)后更改速度OfRectangle。

func wait(factor: CGFloat = 1) -> SKAction {
    return SKAction.waitForDuration(NSTimeInterval(rectHeight * speedOfRectangle * distanceBetweenRectangles / factor))
}

let spawnSequence = SKAction.sequence([wait(), increaseCounter, spawnAction])
let spawnSequenceForever = SKAction.repeatActionForever(spawnSequence)

worldNode.runAction(spawnSequenceForever)

如何定期更改SKActions?