BlackBerry OS is not only robust but comes with so many features I wasnt expecting. Since it’s an operating system sitting in that handset running on same fundamentals like your computer, it might go slow with time because of so many applications open or running all the time.
BlackBerry OS comes with an option which allows you to do memory cleaning. Click on Menu > Options > Security Options > Memory Cleaning.
Memory Cleaning is enabled for the first time when you either lock you handset or reboot it. You would get this message for the first time :
Memory Cleaning is being enabled. This operation may take a few minutes to complete.
Like you can see almost all the places which takes up memory and space can be cleared off during cleaning process making you BlackBerry do much better. You can also manually perform cleaning by clicking on menu button and select Clean All. You need to be in the Memory Cleaning menu for this.