Heatspreaders are generally good if you have a system that is running hot components inside. Its not just what your RAM does that adds heat, but what the components around it do, and how many volts you are running through the MB. Cooling also adds longer life to the components. Most of the better performing RAM chips come with heatspreaders anyway.
I think the real question is how warm is it inside your case? With proper airflow or cooling you don't necessary need heatspreaders, but they do help.