According to our current understanding of physics, as described by Einstein's theory of special relativity, if a person were to travel near or past the speed of light for an extended period of time, several remarkable effects would occur. One of these effects is time dilation.
Time dilation refers to the phenomenon where time appears to pass differently for objects that are moving relative to each other at high speeds. Specifically, as an object approaches the speed of light, time slows down for that object relative to a stationary observer.
From the perspective of the person traveling near or past the speed of light, their own experience of time would be unaffected. However, from the viewpoint of an outside observer, time for the traveling person would appear to slow down.
This means that if a person were to embark on a journey traveling at a substantial fraction of the speed of light and then return to the stationary observer, they would have experienced less time compared to the observer. This effect is often referred to as "time dilation."
So, in answer to your question, if a person were to travel near or past the speed of light for an extended period of time, their subjective experience of time would not change. However, from the perspective of an outside observer, the person's age would appear to have slowed down relative to the observer. This is because time dilation affects the rate at which events occur for objects in relative motion.
It's important to note that reaching or surpassing the speed of light is currently considered impossible for objects with mass, based on our understanding of physics. The theory of special relativity predicts that objects with mass would require an infinite amount of energy to accelerate to the speed of light, making it unattainable. The effects of time dilation and other relativistic phenomena become more pronounced as objects approach the speed of light but are not applicable for objects with mass traveling at or beyond that speed.