This is something specific, but may prove useful. Dave Girard posts a quick tip showing how you can reduce the polygon count of your model over time in Maya using an expression.

Dave shows how to use an expression in Maya’s Polygon Reduce operation’s Percentage setting, showing the effect on an animated Alembic mesh. Dave notes that there are plenty of options in the Reduce operation’s settings that can give you interesting results. For instance, you could do something like polyReduce1.percentage = sin(time)*100 to have the reduction cycle again and again. Plenty of possibilities. Visit Dave Girard over at Polygons Pixels and Paint for more great tips in Maya.