If you are going to have epilepsy is it usually spotted before your 30's?

Quite variable. There is no age when it is distinctly uncommon for epilepsy to start. .
Bimodal. Two age groups are most prone for onset of epilepsy: 1. Birth to mid-twenties 2. 6th through 8th decades of life. But epilepsy can arise at any age whether due to constitutional or acquired causes. If you think you might be having seizures, don't use your age as an exclusion--get evaluated by a doctor.