My opinion is that as long as a bot works fine on current settings (robocode 126.96.36.199 and Java 8), we should "preserve the history". But once it produces random result (e.g. crashing half of the time), we should remove it (until the author should fix it).
Bots known to crash on some machines:
apc.Caan 1.0 dam.MogBot 2.9 sgp.JollyNinja 3.53