AFAIR sessions was moved from prefs.js to the jason file because the later does not slow or slows much less.
Googled the problem. Loading json objects of 38 MB is limit for FF GRE on a 8 GB RAM machine. Good handling around 1.5 MB jason. IMHO that is far less the we use/talk about here.
http://josh.zeigler.us/technology/web-development/how-big-is-too-big-for-json/
Edited 1 time(s). Last edit at 09/01/2015 11:44AM by guenter.