I have been dealing with charging issues that surfaced this past week, as well. I've had my Band since late-March and used it to track my runs (2-3 times per week) since. Before experieincing the charging issues, I had just been charging it when I take showers and occasionally for 30 mins before I goto to sleep. It never dropped below 70% battery power. However, I noticed this week that everytime after I disconnected my Band from the charge cable, the Band automatically shuts off and I have to power it on again.
Yesterday, at around 4PM, my Band notified me that it was low battery, which was strange since I had left it connected to the charger overnight (thinking that it would resolve the auto-shutoff issue). I didn't realize until last night that, despite hearing the Band vibrate when connected to the charge cable, it stopped charging. I had to re-postion it a few times and check on it from time to time to ensure that it was charging. I'm happy to say that I woke up this morning with a 100% charge, but having to keep tabs on it is quite bothersome.
Guess I'll go the replacement route too. I'm going to try and visit a B&M MS store, instead, and see fit they will swap it out on the spot. After tracking daily activities with my Band for the past 5 months, not sure if I can wait 5-8 days for MS to send a replacement.