Even if it does loosen under high heat it’s still going to more or less stay in place, then when it cools down the adhesive will resolidify. When you blast a battery with a heat gun to remove it you just get the glue loose enough that you can pull it away without horribly mangling the battery. It’s still pretty well held in there unless you’re being violent trying to remove it.

How hot a battery should/can get is a whole topic that tends to contain the key words that trigger “UGH!! PLANNED OBSOLESCENCE!!!” stupidity.

But understand that these devices are generally being held in hands or even against our bodies. That is why so much work is done to let them dissipate heat quickly. We will care about the heat long before the components and glue does.

A quick chat gpt says that PSAs tend to soften around 60-80C and Hot Melt Adhesives around 70-100 C.

As for the electronics themselves? They can all run a LOT hotter than people expect. Using desktop PCs (just because I DO know those off the top of my head), a general rule of thumb is to not actually care until a component throttles or the case temperature hits 100F. Individual components have different thresholds (generally anything that is mostly semiconductors is in the danger zone around 100C), but individual components are almost all attached to heat sinks which are “attached” to air which is a really good insulator. So if the air is getting close to 100F (35-ish C if I remember right), stuff is bad.

So yeah. There are definitely cases where you could see the adhesives fail. But they will generally be associated with hardware failures/damage if during use or, more likely, someone leaving their gameboy on the dashboard of a car during the summer.