Hunted West Texas this past weekend (btw, if you get the chance - go! We moved 112 coveys in what was effectively slightly less than 3 days of hunting). We had plenty of dog power, but mine were the only ones limited in time down there, so I ran them hard. My soon to be 6 y/o setter who has had the hypoglycemia problems seemed shaky after about 1.25 hours on the ground on Thursday late afternoon. Spent a lot of time in the box for travel and endured a cold night. Friday, same dog hunted hard in the morning 1.75 hours and then took another run of over an hour that late afternoon. After I put him up from his first run and when we returned to the truck from the second loop (with other dogs) I gave him 1/2 of a pro-plan refuel bar. I didn't see any fall off in the evening run at all. I was kind of scared he would wear down and potentially drop into another seizure, but he was no where even close, despite enduring a cold night in the box. So you might grab a couple of those bars and see if they work for you. I'd be careful, feed 1/2 and give the dog a couple of hours to digest it.
We hunted another full day and 1/2 and he came out of the box sore as hell, tired and beaten up, but when he got his nose on that first covey his energy level was fine and suddenly the pain disappeared.