Oh my gosh, but that's like my P.E. Teacher thinking it will continue forever like that, it has to end somewhere.
My P.E. teacher says "If you ran 9 minutes first time, and you get 7 minutes the last time, you should be able to get 5 minutes this time" That implies 3 minutes next time, 1 minute next time... ON A MILE!
It's more like an inverted square root graph (y=-sqrt(x))