I have an LG G4 as well and absolutely hate it. It overheats almost anytime its on a charger (anker chargers and cables) and running Waze/Google Maps and listening to spotify. I get about 30 to 60 minutes of active use and about 2 hours of standby time on it (sometimes its all day). Bluetooth sucks on it and I have to restart my phone several times of day to free up memory. The camera went from awesome to worse than my old iphone 4 camera. The GPS keeps going out at the worse time and resetting the GPS doesn't help.
It runs hot if the phone has to think. Just the other day, I got a slight burn from how hot the metal power button was and I was just listening to Spiitfy and no other apps was running.
Sadly this was a great phone for about 8 months. After a couple of factory resets it worked good then the issues came back.
My battery isn't damaged yet but since our phones are about the same age I'm guessing it won't be long before mine swells or blows up. I'm constantly watching my phone for signs of danger and generally try and put it near an ac vent when driving or place on a hard cold surface to help cool it.
As to seal batteries, I don't like the idea of a non removable battery (but it won't stop me from getting a sealed battery phone). That means if the battery fails (and yes you can get a bad battery in these new generation of batteries) you have to deal with the cell phone carrier, manufacture, or get it repaired yourself.
I just use common sense when replacing batteries. You need to know what type of battery to get, if its a certified battery or just get a manufacture replacement, and read the many reviews about the non OEM battery you buy. I've never had a problem with battery replacement for any of my tech gear.