When fermenting beer with lacto or bugs as well call it, it is well known the longer the better HOWEVER it does not necessarily mean it will be more sour but NOTHING about wild ferments is certain. What typically happens over the longer time is the acids turn to esters and create fruit notes and this is HIGHLY desirable for beer. I also think the better fermented hot sauces like Tabasco employ this. Easy enough to hide a jar to try. I suspect it might be a balancing act with kimchi and the crunch might take a hit or be a total loss and turn to mush. Much of the REAL good info about this sort of stuff is kept secret... One thing I am supremely confident is that legit kimchi is probably started with the "dregs" of the previous batch to ensure consistency using same culture and speed up production. Another well known thing about fermenting (mainly kraut) is that malted barley is LOADED with lacto AND sugars to start a good lacto ferment. Ground malt is considered a proper kraut starter by many. DYING to try some of this but no time to fool but hope others benefit from the info.