No, I never did, Placebo.

The biggest drawback to the polyphasic is the loss of flexibility in your sleep schedule. The author of one of the essays on it that was linked to in one of these threads even mentioned that it would be harmful to social relationships, since you won't be able to stay out with friends all night, or even be with them for much more than 4 hours.

I did it for almost a week. You're not even supposed to see results in the first week, but a few things happened, one of them important. Around the time I started, I met someone I wanted to stay up with all night... and all of a sudden I valued that flexibility a great deal.

I was also keen on seeing how strongwilled I was, but it ended up not being a question of that. There are benefits and costs to this, and for me the costs just plain outweight the benefits. The largest cost, of course, was an opportunity cost - the cost of forgoing something new.

So, since this is a medium to long term project, I suggest you carefully examine the general contingencies and what all the costs and benefits mean for you, including opportunity cost. A loss of flexibility means that you will not be as able to seize or handle unexpected events in your life. What if you all of a sudden have to travel, for example? Are you interested in meeting new people? This will make those things more difficult. And it is not a question of wills whether or not those things are important to you. It will work best if you lead a structured and predictable life and you want to lead a structured and predictable life.

If it's feasible and you want it, I'm confident that you'll do well. Good luck!