Firefox high cpu usage and flashblock

I've been noticing Firefox using up a lot of CPU lately. At any given time, I normally have about 3 to 4 firefox windows with about 5-6 tabs in each open. But with no activity in them, there should not be much CPU usage. On a hunch, I installed flashblock, a firefox plugin to disable showing flash apps automatically. Instead, it shows a blank rectangle, with a play button in the middle to start the flash app. Installing this made a dramatic effect, and soon I realized this is due to the n number of flash advertisements in different websites. I probably had about 10-15 flash apps playing at the same time, none of them really useful to me. Would highly recomment this add-on.