Outdates flight tracks pile up on screen borders

[dspreitz]

When I leave live.glidernet.org running for a longer while, a significant number of outdated flight tracks pile up on the screen boarders and are not earased after 5 min.

It seems, that when an aircraft is leaving the screen area, it's track is not deleted/shortened according to the defined timing criteria, but processing of the respective flight track stops.

Desriable behaviour would be, that the flight track is shortend accoring to timing criteria although the aircraft has already left the screen area.