To say to an old man “At your age you should know better” in Yunnanese, you say that their beard has gone to seed.
For example, say an old man steals candy from a baby, the mother of the child may well scream at him:
Sī lāo gǔnr, nì fùzi doù qì taìr la, haí nǎme bù dōn shì, zǎge haí qí ge xiào wāwā.
Literally: Dead old villain, your beard’s long gone to seed and you still don’t understand [how to behave], how can you bully a small child?
English: You nasty old geezer, you should know better at your age, picking on a little kid like that!
In Mandarin the phrase “your beard has gone to seed” is not used, but the meaning can be expressed as:
Haí huó bù míngbai
Huó le zhème jiǔ, nǐ zěnme haí bù míngbai dào li?