Similar to your computer there are things which can wake the system from suspend. They can be network activity, WOL packages, timers, or clicking on a mouse or keyboard.
Suspend to RAM is low hanging fruit that would allow the L5 to go a full day or longer. My needs for what could wake the L5 from suspend are very limited. Only incoming calls or text messages. Everything else (emails, chat, etc.) can all wait until I wake the phone again. This is probably the difficult part. Getting the phone to resume fast enough to handle the incoming call, etc.
However with this working the development team doesn’t need to nickle and dime every bit of power savings into the phone. It gives the development team time to focus on other things, like the camera, for example.
With suspend to RAM we have the ultimate high breed of the mobile world. It is basically a tablet laptop with cellular functionality and smartphone format.