I think we have about 10 more doublings of energy consumption before we’re using most incident solar energy. We’re currently doubling energy use every few decades, so that could sustain a few centuries of growth at the current rate. (Like many folks on LW, I expect growth to accelerate enough that we start running up against those limits within this century though.)
We won’t run out of space, material, or energy on Earth in any meaningful sense for a long time (when adding substitution and recycling possibilities), especially as growth seems to be in the services sector. My old post is related: http://blog.practicalethics.ox.ac.uk/2011/11/we-dont-have-a-problem-with-water-food-or-energy/ ; since then, most of the technologies I talked about have gotten cheaper.
The early expansion might pay the large fixed costs, allowing economically viable expansion to start much sooner...
I think we have about 10 more doublings of energy consumption before we’re using most incident solar energy. We’re currently doubling energy use every few decades, so that could sustain a few centuries of growth at the current rate. (Like many folks on LW, I expect growth to accelerate enough that we start running up against those limits within this century though.)