This could be a type of age related dementia. I would be asking my vet about giving Anipryl for aging issues:
Anipryl - Help for Senior Dogs or Cats With Dementia?
What about the side effects of his seizure meds? While most seizure meds cause tiredness...in aging bodies, they can actually have the opposing effect.
Who will take care of him when you're gone for a month, btw...?