Well I deleted 3.5GB of ioncube loaders with no obvious ill effects. Still wondering why so many copies were created.
If this still goes on, try these settings in the php.ini and watch your temp folder ;-)
session.save_path = "/tmp"
session.gc_probability = 50
session.gc_divisor = 100
session.gc_maxlifetime = 1440
session.cache_expire = 180
It makes the clean up a bit faster....