Rather than number of tradelines, I think the AAoA + clean report is more important?
The FICO score breakdown is explained on this very site! See http://www.myfico.com/crediteducation/WhatsInYourScore.aspx
So payment history is 35%, amount owed is 30%, AAoA is 15%, new credit (inqs) 10% and credit mix 10%
So number of lines comes into credit mix, which is very small. Keep amounts owed low, pay on time, and don't app very often, and the high scores will come.