Rubrick, where do you get the ten years? The unmanned missions to Mars have only taken around 18-21 months to get there, so a manned trip should involve no more than 5 years in space (2.5 there, 2.5 back). Mars ain't that far away, after all. Cassini will reach Saturn less than ten years after launch, so ten years to Mars must be taking the scenic route.
The ten years are the worst case scenario which must always be presumed before a firsts-time launch. If you have a small unmanned mission like the lunar rover then you don't have to worry about a leak in the oxygen supply before a launch. This light that candle and watch it fly!
Now there is only a small launch window for Mars because it and Earth are orbiting at different speeds. Miss that aunch window and you are likely playing catchup. If you don't launch then you will have to wait another 18 months for the next realignment. It could feasibly take 18-21 months to get there if all went well but this is nothing like any manned mission performed before so I'm guessing that they'll add a few months on to an each way trip to allow for hitches such as the realignment one above.
Structural damage due to speed is not an issue in space where the vacuum means there is no medium to incur fatigue. The only real risk of damage is landing on Mars and, with its lower gravity than Earth (but denser than the moon) the question of relaunch is going to be a tough one to answer.
