That's a myth, though good advice for the "I don't get high" crowd. If the smoke enters your lungs the vast majority of thc gets absorbed instantly. At most, a second is all that's needed.

The problem is for the people who don't fully inhale, and the smoke never reaches their lungs. Telling them to "hold it in" usually gets them to take a deeper breath. It's not needed if you actually fully inhale.

Contrary to popular opinion - inhale, exhale, inhale, exhale, inhale, exhale.

As you're exhaling vapor (or smoke I guess) your body has processed as much of what you can inhale... but then you inhale again and it'd be pretty weird to assume that whatever is left is exempt, especially if you're rebreathing in some of what you're exhaling.

But if you really want to get higher and be more efficient with your herb switch to vaporization. Heat much above 450F just completely eviscerate the molecules that are working to get us high, so the best thing you can do for your herb is to vaporize it between 360F-420F (or 445f only with high airflow convection vapes), get mid-sized inhales and rebreath them 3-4 times gently. For someone with a low tolerance this will get them noticeably more stoned from "a single hit" since you're getting ~<85% of what you would from smoking the same thing.

Bonus: vaporization is decarboxylation so you get to use the vaped herb as edibles

Take a rip, then follow it up with an inhale to push all smoke into the lungs, then exhale. No point in holding it longer because the lungs are great at absorbing, the trick is to make sure all of the smoke makes it to the lungs.

Don't hold in smoke. That's a way to needlessly harm your lungs.

I vape oil and will take a puff, inhale, hold for 2 secs, then exhale.

I don’t smoke it anymore, I just bake a (hard) cake once a month and nibble on it til it’s gone. It’s good to be able to breath again after fifteen years of daily smoking.

I just hold it til it gets uncomfortable, not really any method. In general, not a fan of coughing, even if it makes you higher (I don't know) I'd still rather avoid it.

I saw a video once on some research that was done. Seems like anything past 10 seconds is pretty much a waste of time, with diminishing returns

As long as feels natural.

I vary, but often I do five-second holds. Not so long that I completely asphyxiate myself, but I'm a bit skeptical of the idea that THC absorbs instantaneously the instant it enters the lungs. Takes a small amount of time, 5 seconds is plenty.