Battery life is going to be affected by many, many variables to include not only what type of batteries you use but also display and keypad back lighting (full time, part time, etc.), how much activity you are receiving, if it's analog or digital (I don't know this for sure but I suspect decoding digital takes more power), volume, and probably more drain for recording.
I had my TRX-1 running yesterday on a set of newer Eneloops and I was receiving almost no activity (I was monitoring for something specific that wasn't being heard much). The radio was still going strong after 10-11 hours but of course it wasn't doing much and as a result the back lights were almost never on.