In previous versions of IDEA I was able to set how many days back the Local History feature would keep the changes in the source files.
For some reason, I cannot find this i
Also you should know that maximum value of this setting localHistory.daysToKeep is 23 (working days).
If you try set this value more than 23, history just will saved nothing at all (after restart IDEA)!
I discovered this by myself by experimental way =)