I'd say 5-6 because besides my legendary enthusiasm, I'm always neutral mooded, I seek balance to nurture my creativity. You know, Eros can't be complete without Thanatos. Without the existential angst, you wouldn't feel the need to ask questions.
(Furthermore, it leaves room for improvements)
Even if I may seem to experience mood shifts on the surface (whether positive or negative), inside, I remain very detached, very cold. Although my friends often describe me as being chronically happy... I've heard that's a common trait amongst ENTPs.
And as someone already said, you cannot really quantify happiness.
"A man who only drinks water has a secret to hide from his fellow-men" -Baudelaire
I have a lot of the things I want, but I'm not satisfied. I don't think I'll ever be.
I also don't believe in being grateful for what you do have to the extent that you shouldn't complain because some people have it worse. If I earn something with hard work, I also consider the right to take it for granted in order to enjoy it to its fullest earned.
The probability that I was procrastinating when I was typing this post:
P(have big assignment due) = 0.6
P(posting on TypoC) = 0.2
P(having big assignment due | posting on TypoC) = 0.7
P(posting on TypoC | having big assignment due) = .......