How long does an electric reel battery last?

It's not really a single answer, because it depends a lot on the model and battery you're using. A common electric reel lasts about 8 to 12 hours of continuous use, but if you use it intermittently during the day (which is normal for most people), the battery easily lasts 2 to 3 days. The best thing is to always check your device's specs, because some good brands deliver longer battery life than others.

A real answer really depends on how much you're actually using it in practice, because nobody's hanging clothes to dry for 12 straight hours. If you use the cart like 1-2 hours a day, the battery easily lasts 5-7 days before you need to charge it, maybe longer if it's a good model. Now if it's heavy use, like from morning to night every single day, then you're gonna be charging it every 2 or 3 days, tops.