yeast two hybrid how long for clones to come out?

[Koi Yau Lam]

I am using clontech's two hybrid system 
currently doing a high stringency selection ( - AHLT )
have been waiting for 10 days already about 12 clones have surfaced but all are false positives
anybody has any idea how long should I wait usually before I can say that there are no interactions?
PS this is a mini project for undergrads so I don't have time to wait too long hence this posting 
Thanks 
Kevin

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