No. Just because you have the capacity for attraction to more than one gender does not mean that your sexual appetite is ravenous.
Absolutely not. The logic behind that stereotype is a lot like assuming that a person who doesn't have a preference for hair color must need twice as much sex as someone who only likes brunettes.
This question is all about the fear that people we don't understand have thinner lines between desires and actions, and the assumption that bisexual people are attracted to ALL men and ALL women, all at the same time. People who aren't straight have a "type", just like straight people. And our willpower is the same as a straight person's. Just like the average straight man and the average straight woman won't try to have sex with every woman or man they meet, bisexual people don't do that either.