I always use a small external battery box now, but I seem to remember getting just about 140-150 minutes on the battery with a 5gb microdrive.
Is this run time with using the internal preamps and A/D, or do you have equipment running into it? I would be running M270 > MiniMe > MT.
This was without running anything into it, The setup was AT 853> SP Battery Box>MT
If I use my UA-5, I always use external power just to be safe. I have a Kingston 2gb CF card, but to be honest I don't think I get much more battery time on it. One time I forgot to turn the external battery power on using the Kingston (I forgot on the first set, and then somehow forgot again on the second set) , and it was showing very low power after the show. Problem is I cannot remember which show or how long, but I haven't been to any shows recently longer than 150 minutes or so.
Like others, I am wary about the internal battery's run times. To me it is my only complaint about the unit, but it seems even in super stealth mode, I can work with the external battery pack, but it is a bit more hassle.