There is no need for the charger to shut off, it will maintain 4.2 volts indefinitely without damaging the battery. More like a battery tender.
Whenever I hear about a charger catching fire on the forums, it's always a trustfire charger. There is a difference between real life and spec sheets. My personal opinion is based on what I've read about the reliability of the trustfire charger and the cases I've heard of where they've continued charging and caught fire.
I would not trust the safety of my family to a trustfire charger unless I was constantly monitoring it and ready to take battery off when charged. Even then I'd hesitate because I'm not the type of person who would remember to monitor my battery.
People who follow my posts know that I'm usually not one of those people who are overly conservative. I do Sub Ohm Vaping against all the POOH POOH's who say it's unsafe. But you have to draw the line somewhere.
Two Rules
1. Do not ever use ICR technology in a Mechanical. LIMN or Panasonic Hybrid only
2. Only use a quality charger and never leave a cheapie like Trustfire or Ultrafire unattended.
Note: Quality Chargers pay for themselves in the long run. They use charging algorithms that are gentle on batteries and will extend the battery life.
You could give me a trustfire charger as a gift and it would go in the trash.
Don't' chinze on batteries or chargers. That's the rule.