Oura Ring is a sleep and activity tracker. Oura Rings website claims that the batteries will lose capacity over time. However, customers are complaining that the unit suddenly stops keeping a charge. The device could initially hold a charge for 6 or 7 days, but after 18 months of use, one customer now has to charge the device every other day. When trying to contact customer service, customers get no response or receive promises to resolve their problems with no follow-through.