iPhone 3G slower using iOS4 multitask enable

My advice if you are using jaibreake iOS4 on the iPhone 3G, do not ever enable multitasking and wallpapers. Because it will only shorten the life of your 3G iPhone .. The reason is: Memorandum on iPhone 3G is very limited. Using Multitasking and wallpapers will only force the memory on your iPhone 3G and cause overheating memory.