Are you using lots of effects? Enable GPU rendering if you are. Again, if your projects require a lot of RAM, adding more will speed up rendering significantly. How long a video is, is not an indication of how much RAM it needs. In Photoshop for instance, 8 GB of RAM is hardly enough, as 99% efficiency is slowing down your entire workflow. by about 100x, compared to 100% efficiency. You generally don't want to bottle neck any component in an editing system. Your main bottle neck right now is your hard drive, not necessarily RAM, even though your projects happens to require more RAM.