Interesting idea, actually! I always consider it to be an unfortunate part of the job; however, I also look at it as an opportunity to allow my best students to shine. Perhaps looking at it in the "glass half full" scenario is the way to go? Meanwhile, I'll suggest a few ways to skirt the issue a bit.
First, it's always more of an issue when I teach mostly juniors because they all come back to me senior year, of course. Therefore, if I find myself getting frustrated with recommendation letters, I simply request a shift in classes at the department level. I've taught all high school grades; therefore, it's usually not an issue for me to switch to freshman English, ... or sophomore. Of course, this requires an understanding department chair. Not everyone is blessed with that.
Secondly, I have a deadline set for students to ask me for that recommendation. I am fairly sneaky in that I have it buried deep within my syllabus/rules, ... but it's there nonetheless. Of course, I have often broken that rule for exemplary students, ... but I have the option of following that rule to the letter for students who "press my buttons," lets say.
Most importantly, I have a few form letters saved for this very purpose. One is a recommendation letter for exemplary students. One is for above average students. One is for average/below students. (This set of form letters is the one single thing that saves me the most time.) I always insert two extra paragraphs: one indicating the students extracurricular activities in school/community and one that gets very specific about the students personality and performance in English class.
Hopefully these suggestions will help a bit. I know, ... it's another one of those unfortunate, extra requirements of a rewarding profession. **sigh**