They keep me cool at work. I see dozens of these on co-workers throughout the day. You are only limited by the battery used. A quality battery will last longer than a fan. I use them 8-16 hours a day, 5 days a week. The first 2 I's lasted a total of about a year (so 6 months each) with the same service life before the motor in them burned out. They last longer than I expected. When these die I will buy 4 more packs.
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