Long? The median is between 4 and 6 days. The 14 days often quoted is the 99th percentile. Can we stop perpetuating this myth?
> asymptomatic carriers makes for easy spread of the virus
Actually, most of the spread comes from superspreading events. Most people with the virus don't spread the virus at all, or spread it very little. True asymptomatic people are far less contagious than symptomatic people (up to 10 fold or so less). Severity of the symptoms is also associated with higher chance of spread.
> It will take something like 75% of the population to be immune (by vaccine or previous infection) to have effective herd immunity.
This is often calculated considering an equally susceptible population (which is not the case) with uniform mixing (same), so it's a very pessimistic estimate. The actual figure might be lower (though not as low as 20% as some "skeptics" say).