Interestingly, if you look at the break-down of how much you spend, for many people a majority of that spend is simply a function of where they live. If you're living in SF, your food+housing+etc is going to be a far greater multiple than if you live out in the sticks.
So I'd say the best way to retire early is probably to get a telecommuting job that pays similarly to your current job, and move to VietNam or Africa. Your expenses should be a fraction of what they were before, and your income should remain similar. Instant years off your working career and no traffic pollution to spoil your day. I think we might be seeing more of this in the future...
Particularly if you can combine that with some kind of passive/recurring income (do consulting from Vietnam, and then also build a product/service from that experience with minimal maintenance)
So I'd say the best way to retire early is probably to get a telecommuting job that pays similarly to your current job, and move to VietNam or Africa. Your expenses should be a fraction of what they were before, and your income should remain similar. Instant years off your working career and no traffic pollution to spoil your day. I think we might be seeing more of this in the future...