Dear Coworker

No, as a matter of fact, I will not cover for you -- again-- as you leave your work area  --again-- to go to the bathroom -- again -- or the break room -- again -- or to smoke your 15th cigarette of the day. 

Why?

Because contrary to what you seem to think, I am not here just to stand in for you.  I do have work of my own to do.  And unlike you, if I don't get my work done, I have to stay late. 

So how about you just stop leaving the line so much, mmmmkay? 

Thank you.

That is all.