Telling you the truth, 4 seconds is enough. The user shouldn't watch the whole vid, he should just hear your product name. He won't pay attention once, twice, but on third time he'll remember even if he don't want.
And then when he'll think "hmm, I want to buy that stuff, what shall I google?" — he'll google your product.



And that's bad cus 99% of free access sites and portals are earning a money with advertising. They should pay for the site, to the personnel and to a hell lot of other things, so when you're blocking the adv, they're loosing money and can went poor, forced to close the site or the platform.