Cleaning up history files

You might all know the problem with long running savegames and the history files that explode into giant files. For example my save in which i am in 2027 has CMT files which are around 500 MB in size. With the add/remove leagues option in FM12 it would mean that the history files could grow faster maybe. It could be that due to the size of files FM needs to keep loaded all the time errors could occur. Is there a way to clean up these files from a certain point without screwing up the complete history of your game? There have been fanmade programs but these screwed up your total game.