This morning I booked a flight DTW-SLC for 25000 TY points plus taxes

The rep has heard about point changes but not about dollar limits. In any case they didn't apply today because the NW receipt lists the base fare as $1007.

I also burned most of my remaining TY points for 2 X 60000 point tickets DTW-EZE in January. I suspect that once they start down this slope, TY points will be like airline FF miles and devalue with time.