As you can read here Microsoft advises against turning on the battery saver all the time. I am very disappointed in the battery life of my Lumia 920 and would like to turn on the battery saver for the whole time, but this 'not recommended' warning holds me back.
Why is it not recommended? Merely because you won't receive any further push-notifications? Or because there might be hardware consequences? (shorter battery life span for example)
The battery life span won't be negatively affected by turning on battery saver. Reducing the current flow out of the battery (which is effectively what this does) might even be better for the battery since the number of charge cycles per week will be reduced.
Microsoft advises against turning on battery saver all the time since it prevents background activity such as checking for updates, notifications, email, etc.
I've found the best way to improve battery life on my Lumia 920 is to ensure as many background processes as possible are turned off. Go to Settings, Applications, Background Tasks.
I recently modified my email sync settings to only sync the past 7 days of emails instead of syncing all the emails in the account, and that made a really huge difference to the battery life. Clearly, reducing the amount of network activity will save battery power.
