Found this on a forum...at the link below...
Phone Idle is the power your phone needs to stay switched on and all the electronics powered up - the memory going, the CPU running at a minimal speed, background processes, etc.

Cell Standby is the power your phone's radio is using to keep in contact with your nearest (usually) cell tower. It will need to check in with the tower every so often, and listen to it in case a call or an SMS comes in.
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I am not somebody who turns the phone off at night in case someone calls with an emergency, which has happened several times.
It sounds like you need to keep it on Standby, in case of emergency, regardless of how fast it drains your battery.

Would putting it on the charger each night be an option, or does the battery need to be run down a good bit before charging?

I've found batteries quite reasonable on Ebay...they are not original equipment, but are 'compatible' batteries. I got one for a Page Plus phone and it was just $1 plus shipping, so I went ahead and got one for me and for a spare.

Sue

Here is a link that might be useful: Cell standby vs phone idle