Does having had a simple febrile convulsion increase the risk for later development of epilepsy (recurrent nonfebrile seizures)?
The risk is minimally elevated, if at all.
At worst the risk rises from the background rate of 1% to a rate of 2% (meaning that 98% of patients with simple febrile seizures do not develop epilepsy).
The risk for patients with complex febrile seizures is higher: 4% to 6%.
Pavlidou E, Hagel C, Panteliadis C: Febrile seizures: recent developments and unanswered questions. Childs Nerv Syst 29(11):2011-2017, 2013.