I have a ~400 sq. ft. area on which I laid 16 inch tile. I finish it
over the weekend. I would like to get started on the grouting today
after work, but I'm not sure if I can get it all done in the time I
have. Is there any problem strength-wise with doing what I can tonight
and then finishing up tomorrow? I know that the bag of grout I use
today may be a shade different from the one tomorrow, but with the bend
in the rooms and the furniture, I don't think that will be all that
obvious.

On a related note, there is one hair line crack that showed up in the
excess mortar showing between the tiles as it dried. It is about 2
feet long and has grown since I first noticed it. It almost seems as
if the mortar shrunk... It is what it is I guess and I may have a
grout line that needs a well placed area rug :-), but I was wondering
if there is anything you can do this late in the game to help it? As
always, thanks for all your help.