Well, that's why that dress took me so long, I was basically doing about 1 hour per day crocheting.
Of course, there were days when I could dedicate more time to the dress, and that's when I would really start feeling the pressure in my back, eyes, wrists. I really don't know how people do it for a living!
I suppose taking regular breaks and stretching is the key.

Good luck with your bigger tapestry projects!