Nick,
I don't think that you can use the jar/jad files although I could be wrong. I found this link http://www.medicalnerds.com/how-to-install-offline-maps-on-your-blackberry-using-trekbuddy-0973/ that explained the installation easier then those on the trekbuddy website.
You need the alx / cod files for the installation I used the DM to do the installation.
As for battery life, i haven't really tested yet, ran it for a couple of hours todsy with no visible sign of battery loss, there is the option to turn the backlight off which I used.