I've had a few bad counts but over the years I've had some super good counts. So I won't complain.
Most of the time I carry a second bucket with chilled 24 or 36 hour water. When I get back to the truck I transfer the water between the 2 buckets and divide the minners in the two.
I freeze a few water bottles. Use frozen water bottles in the cooler instead of ice. If I see the minners dying, I'll rinse the bottle off in the lake then put it in the bucket.