I can tell you the same thing I was told when I started my program: no thesis represents more than 1 year's worth of work. The reason it takes most Ph.D.s 5-10 years (8 in my case) to graduate is that you have to fail, and fail, and fail again for 4-9 years before you find your thesis project.<p>In my case, I started on two exploratory gene knockout "fishing expeditions", both of which didn't turn up anything interesting after a year. Then I crystalized a protein and submitted it to X-ray diffraction, but the results were not good enough for a "high quality" structure, and besides the structure we did find was not particularly interesting. Then I switched to working on NMR structures, but ended up switching universities (politics...there's going to be <i>lots</i> of politics) before that went anywhere.<p>At my new university I switched to structure modeling and worked on a project my advisor suggested for about a year to optimize a modeling routine, but even the optimized version didn't turn up anything interesting. Finally, I landed on a very intriguing problem that could have had far reaching implications. I worked hard at it for almost a year, only to realize that even state-of-the-art modeling was at least a decade away from being able to begin to address the problem I needed to solve. Finally, I returned to a question that a professor had asked me in my first year of graduate school, half jokingly, assuming there was no way to answer the question. For about a year I worked hard at it, finally arrived at a very interesting answer, and graduated.