This is good to know from the point of view of theory. I guess what I'm still curious about is hearing what personal experiences people have had with bacteria during the extraction process, and to what extent they feel that was due to sunlight exposure or other factors. Room temperature extraction is probably the simplest, least technically-involved method of doing what we do. And placing the mason jars in sunlight during extraction has so far been a benefit for me, speeding up the brewing process and getting similar benefits as the heat-assisted method without any additional effort (like intense monitoring, taking up kitchen counter space...etc). As far as risks, after upwards of 80 extractions, over the course of 1.5 years, I haven't had any issues with bacteria personally. In fact the only time I felt a batch of extracts came out a little weak on flavor was during last winter when I probably should have given the jars more exposure.
I just wanted to share my experiences for what its worth to potential newbies looking to get into the hobby but looking for the balance of simplicity/efficiency that works for them. Lord knows I was a long-time lurker, and even now I don't give back to the community as much as I probably should.
I have PG based extracts that are over three years old and taste better now than when they were fresh, have not had any problems with bacteria or anything else....so far. I've never had an extract go bad or develop an off flavor during storage. I store extracts in airtight, tinted glass bottles kept inside a large credenza. Still have no idea how long they'll remain viable under these conditions but am determined to find out. Because all extracts are suspended in a bacteriostatic base I seriously doubt bacteria will be their undoing or even an issue, oxidation will likely be the cause of their ultimate demise. While PG and VG are bacteriostatic (prohibiting growth), PGA (ethanol), is actually bactericidal rapidly killing all vegetative forms of bacteria. It's also tuberculocidal, fungicidal, and virucidal. Even so I don't expect PGA extracts to be as long lived as those stored in PG because I believe over time the aggressive nature of ethanol will, itself, distort/modify the tobacco flavor. My oldest PGA based extract is only around 8 months old so I guess time will tell.
I'm glad you are taking the time to share your experiences, concerns and thoughts with others. This forum is a -gold mine- of information for anyone thinking about extracting flavor from tobacco thanks in no small part to people like you who take the time to share and contribute. I too lurked in this forum for many months before finally deciding to join ECF and participate in the discussions. The information I gained from these threads greatly enhanced the quality of my extractions and personal satisfaction with the NETs I produced.