I have not had a hygro in any of my ice chests
for 6-7 years. I trust my beads and keep them supplied with water.
I don't use one either. and I've never had issues. As long as your cooler is fairly airtight or close, you shouldn't have to worry. The beads will take care of everything. If you want some extra assurance, maybe put a strip of rubber with adhesive backing around the edge where the cooler seals.