[Edit 2016.03.24]: Unfortunately, I did look it up. It turns out that rubato is the speeding up and slowing down of the tempo within a given musical phrase or figure for the sake of expressive emphasis. Real rubato involves no net change of overall tempo: for every sped up bar (or whatever) there is one that is played correspondingly slowly so that when the piece is over, it was no longer or shorter than if it had been played in rigid lockstep tempo all the way through. What I do is shift the tempo this way and that and even change the time signature for a while. The result is more like a Picasso than a Rembrandt or a Vermeer: it never does get resolved. So I can't truthfully call myself a true rubatist.
Unless you look at the whole picture, maybe. By the time my misspent youth has bled into my misspent prime, been superceded by my misspent middle age and lapsed into my misspent dotage, all matter and energy, all speed and lethargy, all diligence and indolence will have been accounted for and offset accordingly, resulting in a net change of . . . zero. Perfect timing. You just have to watch till the end.
I turns out that playing a passage faster causes it to be perceived as louder even though it is not really. This can be handy for expressing expression on something like a harpsichord which has no natural dynamics to speak of.
. . .
Can you misspend your dotage? Can that even happen? It kind of seems like it's out of your hands at that point. Maybe someone could misspend it for you, a conservator or somebody. What comes to mind is a four year-old standing in line to ride a carousel. When she gets to the gate, the man takes the thirty-five cents out of her hand and waves her through, assuming that she wanted to ride the carousel and that the money had been given to her for that purpose. Nobody, including the four year-old, stops to wonder if any of that was not the case. That's how I feel: the cost of my ticket is being taken from me and I'm being waved on through.