Simple partial seizure, 26 mos since last episode, on Keppra (levetiracetam) 250mg once a day for 26 months. What's recommended weaning schedule?

Take your time. It may or may not be safe to stop your medication at this point. I usually wait at least 3 yrs, and if totally seizure free over this time, I check an EEG, and repeat neurological exam. If all is well, would wean over about 3-4 months. But, you are taking exceptionally low dose of Keppra, (levetiracetam) which is likely sub therapeutic. Work closely with your neurologist.