Has anyone ever measured whether toggling WLAN scanning really has a significant effect? According to ajalkane, it's done only every 5 minutes.

Also, does the system keep a list of periodically scheduled tasks? I think there should be some cron-like daemon that takes care of starting the various syncs adhering to the user's settings. If so, can the list be inspected? D-Bus?

This on an N900 but switching it to "never" increased my battery life from ~12 hours to ~48.

Can't say much else than "holy sh*t"

Yes it has a significant effect. Because you won't get online automaticaly (in case of missing rescan) to the "Automaticaly used networks" if your connection is down. No active wifi = less battery consumption. But you should not have services in backgrounf that always need the connection (twitter, skype, auto mail sync...).

One week in rare use ist possible for me too.
N9, stock kernel PR1.3, profilematic and inception - of course ;-)

I forgot to mention the said N9 is on PR1.0

PSM also changes from 3G to GSM.. At least from what I experienced. But yeah, disabling WLAN scanning helps a lot.

had the N9 in the "NOKIA" bag sitting in a corner for a few days as well as carrying it in my coat a couple times with 3G (when available).
run little over 4 days simply with a "empty" standby screen (i have it in its black leather pouch when not in use) and being online (mail, social sites & some Skyping)
after two days +/- i had 11 mAh in idle (& most of the time then, was the 1st time i used it in that charge )
missed to check power consumption before it went out, though

a couple charges back (was mostly at home & used WLAN automatically) it was down to 6 mAh idle but i didn't bother checking how long it run that way) used a Bluetooth keyboard as well, thus that probably burnt the battery down quite a bit

Sometime after a flash idle power consumption rises, I have no idea what's causing this. At first avg idle is 5-6mA and after say a week or two it rises up to 12. I've got backup in backupmenu and usually I restore it every two weeks. This I think is the easiest way to keep avg idle power consumption as low as possible. Oh, forgot to mention, dual gsm mode, wifi sometimes left on, bluetooth is usually on.