The prodigality of God?

I realise that my tally of contributions to this blog is lagging behind others, so I hesitate to come in with a negative comment. However, I am Scottish, so I'll get away with it. I have always been very uncomfortable with the notion of a prodigal God. To me, prodigality means wastefulness, and God certainly is not that. If it is being used as a synonym for 'lavish', then the prodigal son certainly was not that, since his use of the father's resources was lavished only on himself. None of the classic theologies - to my knowledge - highlight prodigality as an attribute of God. This, of course, is not to deny the abundance of God's mercy on his covenant people, from whom he keeps back no good thing. But there is the control: God lavishes mercies on us in accordance with his covenant promises. He wastes no graces, and is abundant for his own glory, even in the afflictions he ordains for his people. Perhaps I need to read Tim Keller's book as a corrective to my theological vocabulary; but the nuances and negative connotations of the word are such that I would hesitate to make 'prodigality' a divine attribute.