As @Keneda understood, it was a question, not a request. It is a question to those young and enterprising people here. If someone can find a solution, I'd quite happily implement it. If not, the question is dropped.
Its time for me to go away and enjoy life, as the rest of it is not much to the time I was present on this planet Earth. 
@alan_g said in Observations on battery life - please share your experiences:
I've replicated what follows from the Telegram Supergroup, as that's no place to collect observations from people using a variety of phones. Hopefully some patterns will emerge that inspire improvements.
I have a Nexus5 and, since 16.04, regularly get over 24hrs from the battery. OTOH I have noticed that there are (still) issues:
- Sometimes it gets to a state that "eats" battery very quickly when not in use. Shutting down (which, in this state often need two tries before the screen goes fully black) and rebooting seems to fix this.
Glad you brought this up. N5 just eats the battery in idle state. Wifi, Data, LTE etc are all off. I tested this matter on Android (stock rom and Pie 9 rom) and the battery didn't drain at all. So, it should be an OS problem. I wrote about that here, https://forums.ubports.com/topic/1958/n5-battery-usage-in-ut-and-in-android
Hope something can be done about this problem. Some apps don't go to sleep correctly, I suppose.
The battery drain problem should have to be looked into in this device, or a newer device to be found, with a known better battery life to port UT to. Android 9 Pie fork for this N5 is doing quite well -- normal usage, few calls, few smses, few looks in the web, the battery had lost only 26% since yesterday 11 p.m (full charge). Now it is 5.15 p.m. Bit more than 18 hours. (Thinking of buying a N6 or N6P to test too.)
@lakotaubp I let the phone fully discharge thrice, recharging until it becomes white. I checked this battery loss for few days. Then I moved N5 to stock Android, just to check how the battery works in it. Its 11.25 now, and N5 with stock Android had lost only 9%, while with UT, I had to start recharging at this time; it rapidly went down. Wifi on, LTE off, no phone calls, no smses whatever, just idling. I am going to check this for next few days with Android.
Btw, this should be in General, rather than Support. There is nothing much we can do to support old hardware. This N5 is made in May 2014, used by one person quite carefully. It took me quite while to find a decent one.
If the battery works quite well in Android, but poorly in UT, we have a problem, not with the hardware. The stock Android is using 3.4 kernel from September 2016. I think UT is using 4.4 kernel.
It took a long time for me to find a decent N5 to try out UT. N5s are pretty old and practically not available in my country in any 2nd hand shops. The other officially supported phones also are not available. I've been searching for one for few months, and finally got this N5.
Installing UT was a breeze. It was different and it was nice. But, the battery use is not that good. Fully charged in the evening phone lost about 40% overnight. Checked at 9 a.m.
Now that I have this N5 and had got UT on it, I thought of reinstalling Android back to have check. Reinstalling stock Android was quite easy. Battery lost only 8% by 9 a.m. the next day. In both situations, WiFi was on, but the LTE was off. And, it was both stock UT and stock Android.
I found the answer to my own question. There is a light on the bottom of N5 that keeps flashing, and the envelope icon on top becomes green.