It took me about 3 days to sand 30 sq m. of floor with a Rotex 150 - about 2 hours at a time.
breaks mainly because of backache & boredom...
I'm very happy with the finish, but would echo the points about knee pads and ear defenders (actually iPod & sound isolating headphones)
I took it to 80 grit (180 resulted in too slippery a finish) so I ended with 80 on an RTS 400 just to ensure the last sanding was along the grain.
I'd have paid more than the cost of the tools to have it done professionally, so very pleased