I searched and eventually found the fix in the registry of all of the WM5 / WM6 devices on sale in NZ that disconnects your data session if not used for a set period of time. knocked my head against the wall abit first but stoked i kept searching.
No software apart from a specified Reg editor is required. Simple and increased battery and performance when using exchange or pop3 auto sync etc.
PM me you want the software name and registry edit.