I thought I'd come back here to report on the battery usage. After some users reported 20-30% drain a day, others claimed that 3G or 4G drains the battery faster and others still suggested to turn off GPS, here is the result of my tests running continuously for the past three months:

• My battery lasts 24 to 48 hours on average.
• 3G or GPS have a negligible effect. I do not care if the phone lasts 24 or 25 hours between charges; if the difference is so small, I can as well leave everthing on all the time.
• The only thing that makes any difference at all is my usage pattern. If I leave it on standby, it can last up to 5 days. If I use it, it lasts about a day. 2 hours browsing equals about 2 days on the shelf.

A very representative example as of last Saturday. The configuration (what is on, what is off and what is not installed at all) as per this post. All times are approximate to the nearest 10 minutes:

• 06:50... 100%. Taken off the charger. Spent about 20 minutes browsing, then put in the pocket and took the kids out.
• 08:30... 84%. Just remembered to check the battery level.
• 10:00... 74%. Started using it again to make pictures. Took 12 pictures and 4 short videos. Did not shut the camera app, just locked the phone with the power button and put it back in the pocket. Forgot to check the battery level at the end.
• 14:50... 17%. I noticed the pocket was suspiciously hot. It was the phone. With the camera app stil on standby. I shut the camera app.
• 18:20... 11%. We gradually made our way home. Plugged the phone in the charger.
• 20:00... 100%. Went to run the bath for the kids. Spent about 10 minutes browsing while running the bath.
• 20:10... 94%.

With the exception of the camera app running and nearly melting the phone, this is pretty much the common pattern. 3G or GPS makes no discernable difference, but each minute of browsing costs about 0.5% of the battery charge.

Meanwhile my wife's Jolla, sitting unused on the shelf, needs a recharge about once in a fortnight.

The only conclusion I can make from this is that those who claim less than 30% drain a day can achieve that only by keeping it standby all the time and not actively using it at all.