I agree. If you have exceptionally good service, write a letter of praise. If you have exceptionally bad service and have a suggestion of what the airline can do about it, either to compensate you or to fix the problem so others won't have it in the future, write a letter of complaint. But you shouldn't be writing "many" letters in any given year. On average, most people will be performing about average, so you shouldn't be having HUGE numbers of plaudits and groans to hand out.

The OP's policy to wait 48 hours before writing the letter is a good one, but if your calendar shows that you have written more than a couple of letters a month (or maybe even every three months) to various business handing out praise or complaint, then maybe try sitting on the letters a further 48 hours before you mail them. Sometimes if you think about it, you realize your letter just sounds...petty.

Some people carry small gift cards for $5 or $10 at Starbucks and give them as instant "thank you's" to FAs who perform exceptional service. I guess I've been too shy to do that. But I'm sure that's a nice boost to the good ones. It's a little more challenging to figure out what to do about someone who is obviously stressed or demoralized. Honestly, when I've noticed an FA who seems visibly stressed, I just try to stay out of her hair. As the other poster said, we can't do anything about the labor issues that are taking such toll on salaries and benefit packages.