"Don't expend more effort than they are" has actually long been a good principle to have internalized. Someone done only cursory research before asking a question on a mailing list? Give a cursory answer. Someone obviously spent hours trying to figure things out on their own? Give them a good chunk of your time. Someone on HN responding to you with single-sentence responses? Either don't respond, or respond in kind.…
"I have made this longer than usual because I have not had time to make it shorter." - Blaise Pascal.
The length of the response doesn't indicate effort.