Diarrhea & G tubes

So here I am on my weekend off thinking about work: my question for you: I was taught in home care to only have 4 hrs of forumula at a time in the tube feeding bag to minimize bacterial growth. Place I work at now is filling the bag for the whole 8 hour (recently changed to 12hr) overnight pump infusion..... not on ice or anything. Cans are at room temp. The pt also has chronic diarrhea.... I just now thought that diarrhea may be caused by this tube feeding practice. The MD has assessed the diarrhea many times before and adjusted pt drip rate, forumula type, meds, added benefiber, etc. On the can for the forumla it states to 'refrigerate after opening' but does not state how long it can be safe at room temp. I would imagine that regular food standard practices would apply.... I'll get a trial going and get the routine changed to fill Q 4hrs when I go to work tomorrow but I wanted to know what your thoughts are. Is it common practice fill the bag up for the 8-12 hour infusions or do you replenish in 4 hour increments? (The pt does not take anything PO because of aspiration and has had the tube for over a year.) Thanks!