I had to edit the thread title, please remember to ....(from our Forum Posting Rules)......
Use a Descriptive Title
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Mostly it will be performance, the berry can get bogged down and operate more slowly if you have too many emails, HOWEVER the BB you have does have a good amount of process memory (the BB's equivalent of RAM) so it is not as much of an issue as it was with older BBs.
yeah it is a performance issue. When you are limited in RAM, it will try and shuffle programs around in memory to make more fit. All of that takes processor power which is wasted battery.
Newer BB don't have this issue as much as older ones. I had a pearl, that when it was low on RAM it would only hold a charge for about 4 hours. When it had plenty of memory, it would go for 8-14 depending on usage.