The amount of statistic data where increased in three steps:
For Germany data is available since 04/2008, for Europe since Dec. 14th 2009, and for the whole world since July 26th 2010.
Flights are always collected with departure and destination airport of the collected region. So you can find flights from german to foreign airports already since 2008, but e.g. no flights between american airports.
Of course you already should have departed or arrived at the airport. Diversions are only collected when the flightplan have been changed for the arrival airport, because I check the coordinates when departing/landing.
Another requirement is that you donīt disconnect immediately after landing. The data stream is available only each two minutes.
Because I donīt have direct access to connection data, the times are only collected from the VATSIM data stream. So I can only check every two minutes if a station is still online, and then assume that there were no disconnect between two updates. Also the data stream ist not a 100 percent available service, so server or network errors may cause different values.