Statistics from studies involving millions of patients the world over show that after the kind of head injury received by you, the incidence of further epileptic fits is highest during the first year after the injury. The next peak is after the second year. The third peak is after five years.
If you do not get another fit whilst on the medicine prescribed by your doctor over a year, the chances of your getting a further fit are low. This is the reason why your doctor wishes to gradually taper off the drug after prescribing it for a year.
Premature stoppage of the drug may spark of a flurry of epileptic attacks that would be very troublesome to you.