He is over the hill, you know.

The road descends slowly.

The road dips suddenly.

The road declines sharply.

Business is declining.

For a girl, after 30, it's downhill all the way.

The weather is supposed to go downhill starting this afternoon.

The weather will change for the worse this afternoon.

By September the burst in spending seemed to be tapering off.

The hill slopes downward to the river.