Can lightweight coolers keep ice for two days?

Yes, but only with the right prep: pre-chill the cooler and use block ice instead of cubes. A good soft cooler like a Yeti Hopper or Engel, or a thinner rotomolded hard cooler like a Pelican 20QT Elite, will hold ice for 48 hours. The tradeoff is durability and price — they dent easier and soft ones can leak if the zipper fails. For car camping or a weekend trip, they’re fine, but don’t expect miracles from a cheap bag.