I much prefer 4:3 screens instead of stupid rage of 16:9 (16:10 is only a slight improvement). I do not have a choice though than to deal with squishy screens at work and at home. Further, you may have a huge monitor(s), I do not.
I use large font sizes (~20 pt in browser, ~18 px monospaced font in xterm); on MS Windows I increase the dpi instead by about 25%.
I generally follow 80-character line length limit. When using two vertical windows (as in vim :vsplit or vimdiff) even that limit becomes too large. I often not care for the limit in case of a longer string. Then again I tend to fragment a string around punctuation marks, (semi)independent clauses, after each sentence, etc. if possible.
When printing (in monospaced font at size 14 pt), limit is around 68 characters. If I were to generally use a limit larger than 80-character, a (temporary) reformatting would require more time.