The first Starships to Mars will launch in 2 years when the next Earth-Mars transfer window opens.

These will be uncrewed to test the reliability of landing intact on Mars. If those landings go well, then the first crewed flights to Mars will be in 4 years. 

Flight rate will grow exponentially from there, with the goal of building a self-sustaining city in about 20 years. Being multiplanetary will vastly increase the probable lifespan of consciousness, as we will no longer have all our eggs, literally and metabolically, on one planet.