You can get by on charm for about 15 minutes. After that, you better know something.

The line contrasts first impressions with lasting competence. “Charm” stands for social ease, charisma, and the ability to win quick goodwill—useful for opening doors, interviews, or introductions. But the “15 minutes” suggests a brief grace period: once the novelty of personality wears off, people look for substance—knowledge, skill, preparation, and results. The quote functions as practical advice about credibility: likability can start a relationship, but expertise sustains it. It also implies an ethical dimension: relying on charm alone is a kind of bluff that will eventually be exposed, whereas knowing something earns durable respect.

1) “You can get by on charm for about fifteen minutes. After that, you’d better know something.”
2) “You can get by on charm for about 15 minutes. After that you better know something.”