Same here on the time (42 years). I am on 600 mg per day along with 800 mg of Lamictal (very high dosage). Except occasional auras, I have been mostly seizure free for 15+ years.
I did not start off with cramping. Mine was coordination issues. As I understand it, your boday naturally knows where your limbs are situated around you without optical input. I am losing that ability and need vision to stay balanced. Darkness makes it worse. Going down stairs where I can't see my feet, is probably the worse and I am very careful with that.
When they put a tuning fork on my ankle, I feel it touching me, but no vibration. I feel the vibration on my knee.
I was Dilantin only for about 25 years and still had occasional (but strong) seizures. Then my neuro added Keppra for 5 years, which I eventually had to leave because of emotional issues. Been on ever increasing dosages of Lamictal as an adjunt to the Dilantin for over ten years now. Good control.