DeletedUser410 You might want to use Google's web tool to find out if your battery is affected (not all 6a batteries are).
If you already have 500 cycles and plan to keep using the device the same way until it goes EOL it might make sense to change the battery anyway.
DeletedUser410 I have read that before catching fire some things should happen:
1- phone overheats
2- phone gets swollen (due to battery increased volume)
3- possible noise of small cracks of the screen
Basically it is not something that just happens out of the blue.
Those signs would all be good indications that the battery is in bad shape (though with heating it depends on whether the load on the device is enough that it should be warm). However, I don't think there is a guarantee that the situation is safe for these batteries if none of those symptoms are present.
Since Google's software change for the affected batteries caps the amount of charge, you might enable the 80% charge cap manually.