How Long Should Medications To Control Epileptic Attacks Be Taken?

my husband is epileptic he was taking valprin 500 bd ater taking 7 months he got 2 attacks in night
now doc has added zonisep med with valprin along with dat ulyses150
he also had delayed hypersenstivity 2 dilantin.he is been epileptic for 1 year,now he has allergy 2 ulyses he has stopped it.
for how many years he has to take med and why he had attack after taking medicines also.till now he has 6 attacks out of which 4 were during sleep