Age always goes up and never comes down. Aging is irreversible. This question is meant to be a riddle and does not require application of the principles of physics. A person can only grow old and never younger.
There are other things such as petrol prices and inflation that seem to be going up all the time. However, even petrol prices and inflation tend to reverse occasionally. Food prices are on the way up, but when conditions are right, food prices may also come down a little. Individuals with an inflated ego appear to never let go of their ego. However, even the ego may take a bruising sometimes. Despite all medical advances, time and age march on relentlessly.