I feel like the way I do 80-column indication in Vim is incorrect: set columns=80. At times I also set textwidth but I like to be able to see and anticipate line overflow with the set columns alternative.

This has some unfortunate side effects -- I can't set number for fear of splitting between files that have different orders of line numbers; i.e. < 100 line files and >= 100 line files will require two different set columns values because of the extra column used for the additional digit display. I also start new (g)Vim sessions instead of splitting windows vertically, which forces me to use the window manager's clipboard -- vsplits force me to do set columns every time I open or close a pane, so starting a new session is less hassle.

How do you handle the 80-character indication when you want to set numbers, vertically split, etc.?