Share your experience!
Need to know how to fix stamina mode when it doesnt work & does my phone need to go for repair or no. I tried doing a force stop on the eco mode application to fix it, but is there a permanent fix?
Solved! Go to Solution.
http://talk.sonymobile.com/message/446354#446354
post 12 - might help you understand what stamina is
Right now there is no solution for the stamina mode bug unless they have fix it in 10.1.A.1.434 update. If problem still arise wait for 4.2.2 update. 
Without knowing what problem you have with stamina mode it's hard to assist you but i recommend that you start by reading the explanation of how it works here: http://talk.sonymobile.com/message/154243.
not fixed it this update either...
@Rickard,
The problem is sometimes randomly the stamina mode figure won't change whether toggle it on or off.
For example: when I turn it off it will say 1 day 2 hour, but when I turn it on the figure is same.
Obviously, there's a bug which causing the figure still same.
When I first got mine, it worked fine, but now I have to do work around temporary solution by go to Setting -> App -> Running -> Eco Mode Controller.
Force stop it, clear the data, and restart the phone.
Then the figure will change again when toggle on or off the stamina mode
http://talk.sonymobile.com/message/446354#446354
post 12 - might help you understand what stamina is
Check the post by GeoffH about how stamina works. Simply put, if the estimated standby doesn't change when you enable stamina that's because stamina has determined that based on your previous usage of the phone it can't do much to improve standby.
@ Rickard and GeoffH
This is definitely a bug when the stamina mode figure is same when toggling it on or off.
I just did a simple test by not whitelisting 'LINE' app, was using mobile data, then when I sent message using another phone I still can receive the message.
However, when I reset the eco mode controller, the figure back to normal and I tried to send the message again, but I didn't get the message since I did not put 'LINE' in whitelist.
So simply, stamina mode NOT working properly due to bugs!
and yet another post to help you understand how this works - follow the link and read my post, if you still don't get it - use a rope
http://talk.sonymobile.com/thread/125245?tstart=0
and yes experia blog has a post from someone that doesn't get it either
and just now is the first time I've ever read that post by Johan - glad to see that we are saying roughly the same except mine is more detailed for the really challenged
that post is only the repetition of another explanation of stamina mode.
the point I'm trying to say with my previous post, when the figure of stamina mode doesn't change either turning it on or off, applications such as 'whatsapp', 'line' don't work properly as I still received the messages coming without listing it on whitelist.
clearly, there's a bug preventing the stamina mode to work properly.
if you still don't get it - use a chain