I've read a lot of the replies already posted here about this being a problem with the older units. Mine is a couple of years old and has powered itself down after 30 minutes pretty much forever. I'm guessing that the unit is out of warranty now, but I have to wonder why this is even happening? Since you made changes to newer models my guess is that there is/was some sort of defect causing this. In my case, there is nothing obviously wrong with the battery - it charges and holds a charge perfectly. The 30 minute sleep mode shut down even occurs when the unit is plugged in and getting audio from an iPad or iPhone. Otherwise the unit sounds great and I enjoy using it but having to reset the thing every 30 minutes is certainly annoying. At the very least can these be returned for repair?