A treasure knife does not age. This is a great idiom that is almost always used to describe old people who’ve still got it. What better example could there be than good old 史恩·康納萊 (shǐ ēn · kāng nà lái).
wǒ hái shì yīyàng bǎodāowèilǎo
I’m old, but still as vigorous as always
tā suīrán niánjì dà le dàn yǎnjì guò rén zhēn shì bǎodāowèilǎo a
Even though he may be old, his acting skills are still better than most, he’s definitely still got it!
The way you translate this idiom into English is really up to you, it really depends on who you are talking about and the situation. Just remember to capture the feeling that the person you’re talking about is still 厲害（厉害 lì hài） regardless of their age.