In order to have a sustainable presence we need to do extensive surveys and establish significant surface capacity for use of in situ materials. Sorry, but there is no way you can convince me that emphasizing sending men and all the stuff it takes to support them at this early stage is going to achieve sustainable presence in the quickest time frame. And your 1.5 year mission is how much actual scientific exploration and how much transport, maintenance, and survival overhead? Look at the ISS. Look at the absurd cost per science experiment/hour. 99 percent of time is spent on survival not study.

Do we currently have sustainable presence in the deep oceans? No, because it would be ridiculous expensive and for what? We send our robotic probes as extensions of ourselves and return samples and visuals (in more spectrums than the eye can see). In the same fashion we could provide the experience of exploring mars to millions through robotic extensions, versus a handful of humans that get to experience it truly viscerally. I certainly think it is a good tradeoff (at least for the near future).

I can't see how anyone who actually approaches the quesitons with a modicum of logic and reason can fail to see the enormous cost/benefit tradeoffs favor a very strong emphasis on robotics for the near term. If we can ever significantly lower launch costs then the equation changes rapidly, but until we have a space elevator or a very major breakthrough in propulsion technology I don't see launch costs lowering much for a very long time.

p.s. Just saw today where Hitachi has made breakthrough in hard disc storage that will allow quadrupling of todays storage limits by factor of 4. These kinds of technology leaps supporting robotic development are constant, but man is staying the same. Robots 25 years from now (when we are contemplating manned visits to mars) will be vastly superior to current technology. Also they will be applicable to Asteroids, Jupiter, and Saturn Systems, and even Venus. Just like the oceans, tele-presence will be close to the real thing, but stupendously less expensive.