I have a question about the trust system , Let's assume that I'm NOT the DefaultTrust and I left positive trust for someone , it won't really affect his trust score at all .
But if after few months I'm on the DefaultTrust , does my positive trust that I gave him affect his profile instantly or I should give him once again so it works ?
It affects his profile instantly.
The reverse has been evident in many cases - as soon as somebody gets knocked off default trust, the trust ratings of that member cease to be reflected on the profiles of users by default. So when you get added to DT, it should work the same way.