Make sure you "marry" your batteries. I even went as far as to take a sharpy and label mine in pairs. Always use them together, they should always be charged together and used together. This way they wear down at the same rate. Having one being more drained than the other can be bad. But then also just overall lifetime, over time batteries become less efficient, they lose their charge quickly and such, keeping two batteries married keeps them at the same age.
With that always use identical batteries, you say you're using VTC4's well you can't really beat that for power output, as I understand it those are one of the few 30amp rated batteries (though there seems to always be a ton of debate about actual performance of things), Stick to those if you need the higher amperage, and Samsung 25r or LG HG2 for longer life. Stay clear of companies like Efest or anything other than Samsung, LG and Sony. The companies like Efest simply buy batteries from those 3 companies and rewrap them to market themselves. The true ones cost the same or even cheaper so why bother with the others where you don't really know what you're getting?
Keep an eye on the heat of your batteries/mod. Notice something weird, STOP. Your regulated mod has a bunch of protection built in to prevent issues, but they aren't foolproof, if you notice something stop and investigate.
A lot of the blowing vapes were from overcharging and forgetting with bad batteries/chargers... basically negligent stupidity. Or on Mechs where the button is held down for a long time (not an issue with regulated mods with their 10-15s cutoffs usually)... again though negligent stupidity. Just some basic common sense and attention to detail and it shouldn't be any more risk than stepping outside your house.
