The Charge and Charge HR, same as the Surge were utter garbage. Bubbling bands, poor quality. Just bad! I mean, really bad! The Alta, Charge 2 are very high quality and built well. Same for the Flex 2, well designed, well made. So, they have improved a lot.I’ve had a few Fitbit Ones (they’re easy to lose) and they do last about 3-4 days between charges. I’ve also had three Charges and a Charge HR (I was given the first Charge and the rest were warranty replacements as there was a fairly serious design flaw so they only last a few months) and the battery life on all has been very random (1-4 days, battery warning only when it really needs to be on charge). As a result, ive never run out of charge on my Apple Watch but frequently have done with Fitbits.
For sleep tracking though, honest, if you have an Apple Watch buy a Xiaomi miband. £5 now and it syncs to health. Super light, HR sensor, 30 days+ battery life. Feels like an apple product and is better than all the apple watch apps.
https://www.gearbest.com/smart-wristband/pp_263275.html