Nope. Doesn't make the slightest difference.
Some more details. Say I've got a text box that's 47 wide, and 17 high.
I go and change those dimensions to 60 x 20. Then I go and edit another box. When I click back onto the first box it's back to 47 x 17 again.
Another thing I can do is change the box dimensions from 47 x 17 to 60 x 20, then go in and customise the text. When I come back out the box has returned to 47 x 17 again.
Surely there's something simple I'm doing wrong, or that I've neglected to do? Can someone put me out of my misery?