There's no rule about elders or superiors, apart from the obvious fact that if you telling a superior/elder what they should do (which is the basic meaning), you should be able to back up your opinion.
Generally, it would be more polite to say something like: "Wouldn't it be better to ... ?" or "What do you think about ... ?"
"Homer, maybe you better take Milhouse home." Note that Marge? here says "maybe you better..." which is also a polite way of saying it.