Some quick answers -
(1) If it takes 12 hours to charge a battery, you're charging at way too low a charge rate. I use Panasonic CGR18650CH batteries a lot, with an Xtar VP1 charger, and charge them at 1000ma, 1 amp. The charge time is, at most, three hours. If you are really concerned about a fire from a battery or charger malfunction while charging, just put the charger and batteries in a cast iron pot.
(2) A charged battery can sit around, fully charged for a year, or even longer. It might lose a little capacity over that long a time period. After a year, a quick charge on an intelligent charger will top them right off again. Damage doesn't occur to a lithium based battery until the cell voltage drops to about 2.7 volts or lower. Even them a good intelligent charger may be able to "bring them back".
(3) Lithium batteries, like the ones used for vaping, should be stored in a plastic or other non-conductive case. If your batteries don't come with a plastic case when you buy them, cases are available from many vendors and are very inexpensive. They should always be in an environment where they cannot be short circuited. Many battery horror stories happen because people put them loose into a situation where they get shorted out. As an example, the change or keys in your pocket can short them out. These batteries are capable of extremely high current, power, output and can quickly overheat enough to cause a fire under short circuit conditions.
(to be read at double speed)
Just my opinion, worth what you're paying for it. Your results and mileage may vary. No warranty or guarantee is expressed or implied. Proceed at your own risk. The end user agrees to hold the poster harmless and without liability. I am not a doctor, scientist, chemist or physicist and hold no academic degrees, nor do I play any of them on TV.
