Re: @boxplayer - "Nobody uses it..."
I stopped trying many year ago. And the reason is: if I manage to convince them, and it fails, my head will get chopped. If we succeed, I would be "spared".
So the thing to do is just tell them in writing: we need to do this, and it will getting more expensive as time passses by, no definite timeline right now. And that's it.. when its time to do it, ask for the money as where will be a bid damocles sword, and money will happen. Oh, and as they know they knew, they will probably be nice about it.