Any kind of W-LAN access will kill the battery, esp if it is reasonably constant which connected to SIP thru W-LAN seems to be. I have had my battery die from fully charged after 6hours by leaving Truphone connected.
See the battery "bible" thread about setting the Tx power to 4mW not having any affect, I wonder if the current f/w has a bug and ignores this setting?
I disagree. I have Truphone running all the time and do not notice any appreciable decrease in battery when "connected" /"registered" through my home network. However, when out and about and "roaming", I'm not so sure. Some days there is no difference, other days I think it does, and I've not worked out why. I tend to switch roaming off and only let it register my home network, and then manually connect when I know I'm in a wifi zone.
One thing I should add is that I had to disable my W-LAN "power saving" option for my phone to work properly with my router, so this might explain why, when I see that W-LAN icon up on the screen the whole time, that my battery life is down to about 6hours only.