If you're storing video only for offline viewing with minimal seeking, you can increase the iframe seperation, but if you're streaming this video, you'll need to pay the cost of including iframes to allow clients to seek or recover from dropped packets.
There's a tradeoff between skip/fast forward fidelity, streaming delay, and iframes. If you're not live streaming and don't care how easy it is to skip around the video increase the iframes inverval as much as you want and watch the bitrate melt away
This is mostly used for TV broadcasts where you don't want the whole keyframe to get lost because of some brief interference. It's also good because it lowers peak bandwidth per second.