Hi J's Mum,
After 29 years of experience with epilepsy, I can tell you this:
Sometimes a seizure can start very deep within the brain and will not show up on an EEG.
In many cases several tests will be required to get a reading ie: Blood test, CAT scan, MRI, PET scan, etc. and could still be inconclusive.
In a lot of cases you could have a series of seizures in a short period of time and then no more for several years. It's almost like saying that it goes in to remission. Epilepsy doesn't go away but it is treatable.
Then something will trigger another one, like fireworks, sounds, smells, STRESS or a combonation of them all.
My advice; If he's planning on getting a drivers licence and sinse the meds seemed to work ~ STAY ON THE MEDS as an insurance policy. Better safe than sorry.