IDEA slows down after a while

hi all,

I tend to leave my IDEA open (at work) overnight, usually for days at a time.  I've noticed that it becomes very slow and unresponsive after a while.  Typing becomes very slow and I can see the cpu usage spiking any time I do anything in the editor.

I don't recall this happening on IDEA 11, but it has been a long time since i've used it.  This is IDEA Ultimate 12.1.6, but the problem has existed for at least a couple of minor release.

Anyone have any suggestions?