On YouTube you have five seconds before the skip button.

Not necessarily. Clear audio, a strong first line and an honest demonstration outperform expensive production with a slow opening. Poor audio, however, will sink a campaign faster than poor visuals.

Look at assisted conversions and branded search volume, not just last-click. If YouTube spend rises and people start searching your name more, that is the channel working even when the conversion is credited elsewhere.

As long as it stays interesting and no longer. For direct response, fifteen to thirty seconds is common. For a complex product, a longer video shown to a warm remarketing audience often outperforms a short one shown cold.

As a starting point, yes, but the platforms reward different things. Meta creative often assumes sound off and vertical format; YouTube in-stream assumes sound on and horizontal. Reusing without adapting usually underperforms both.