The denaturant makes the alcohol taste bad. When a denaturant is added to alcohol it is called denatured alcohol or Alcohol Denat. Denatonium Benzoate is a common denaturant. It a quaternary ammonium compound that is considered the bitterest compound known. Quassin, Brucine and Brucine Sulfate are bitter alkaloid compounds obtained from plants.
Well, there can be some irregular pacing, breathing before the seizure. That can last from a few minutes to 30 minutes or more. The seizure itself should not be longer than a few minutes. Anything over 4-5 minutes is a huge risk for brain and body injury. After the actual seizure, a pet can remain disoriented, but they are at least responsive, for another few minutes to hours.
I have seen dogs get pretty zonked out by potassium bromide...but not for 3 days although it's certainly possible. I have seen dogs have brain damage after having one long seizure. I've had cases where we couldn't stop a seizure and an animal seizured for 30 minutes and then was essentially brain dead after that. But I can't say that I have seen an animal have brain damage after cluster seizures.