Depends on whether you consider the extra columns to be yours or those of your audience. If they're yours, use them however you want. If they're your audience's

Depends on whether you consider the extra columns to be yours or those of your audience. If they're yours, use them however you want. If they're your audience's, then stick to the 80-column standard so your readers can tile standard-sized windows the way they want on their large monitors. Especially important for side-by-side code diffs.