The storage and using of Accumulators depends on the Type of Accu.
The older NiCD or NiMH get´s Memoryeffect if they often discharged not completely,
some Chargers are able to discharge the Accu befor charging to avoid the Memoryeffekt.
The newer LiType Accus ( used in most of our Cameras ) dont have this Memoryeffekt an don´t
like to be full discharged - fully discharging reduces Lifetime AND Capacity.
( Like the Accumulators in the Car ( LeadAcid Type ) )
Storing in a cold Place is good for long Time Storage.
LiType don´t like very hot Environment ( especially LiPolymeretype ( Car in the Sun...
Best for LiType ist Storage not fully charged.
When using: Cold Accu has to be warmed up first to geht more Power ( softly ! ) .
I would cycle threw the Accus to use them all the same Counts.
If possible don´t charge below 20%.
As written above in this Topic: Cold Storage reduces the Speed of chemical Procedures
inside the Batteries .
In real Cold Environment it´s an good idea to use NiType Accus if possible.
But... i´ve got an old Powershot G2, the Accu was used loveless for over 10 J
But now he ist death ! - So this is the only Reason to by an DSLR