Most of the issues with venting, fires, explosions of li-ion cells have to do with:
- Low quality cells.
- Low quality chargers.
- Multiple cell configurations, generally in series (but not necessarily so).
You’re taking care to purchase high quality products, so that takes care of items 1 and 2. As to number 3, you can ask questions about what precautions to take before you start buying multiple cell flashlights.
For single cell applications, there is some risk of discharging your battery too low and from physical abuse. As far as physical abuse is concerned, what is there to say? Don’t stick them in a microwave, don’t submerge them in water, don’t puncture them with ice picks, don’t use them as door stops, don’t use them as dog chews. :evil:
As to running them down too low, it’s hard NOT to notice your battery drain when you’re actually using the flashlight. By the time your battery drops down to 3.4V, you’ll notice a significant drop off in brightness. (At the medium and high levels, anyway. On moonlight, you might not notice.)
You want to stay above 3.0V to prolong your battery life. And 2.7V is the threshhold for safety concerns. Anything below 2.7V incurs a (small) risk of internal chemistry changes that theoretically could lead to a situation where it would be unsafe to recharge the battery.
For your BLF A6, its driver has a built in low voltage protection that will cutoff the batteries when it drops somewhere between 2.8V and 2.7V. So, draining your batteries beyond that isn’t an issue.
So, your only concern in using unprotected batteries would be (1) in letting others use your flashlights, in which case you’ll have to evaluate the risk of what they are doing, and (2) in situations where you are not actively using your flashlight.
For me, this latter situation arises in two cases. First, there are flashlights that have what is known as parasitic drain. Due to the electronics within the flashlight - whether that be from battery monitoring circuits, mode memory, or tailcap lights - the flashlight continues to use current, even when it is turned off. Fortunately, many of these flashlights have built-in low voltage cutoffs. Unfortunately, the parasitic drain may be so small that it doesn’t begin to trigger the cutoffs. 
The second case is when I intentionally or unintentionally leave my flashlight on, say I leave my flashlight on when working on my car in the garage or I accidentally click the switch when fumbling through my duffel bag.
Last word of caution. You should never charge your batteries unattended. While the risk is minute of anything happening, it is an unnecessary risk. Be attentive when you’re charging your batteries. :exmark:
BTW, I have 30Q flattops in all three of my BLF A6’s. 
