I actually don't know much about electronics, but I have a speaker system where capacitors are known to get hot then the sound starts to crackle after about 5 hours.

Here's some info from the web though...

As electronic devices become smaller and lighter in weight, the component mounting density increases, with the result that heat dissipation performance decreases, causing the device temperature to rise easily. In particular, heat generation from the power output circuit elements greatly affects the temperature rise of devices. However, in applications (switching power supply smoothing, high-frequency power amplifier output coupling, etc.) where large currents also flow in capacitors, the power consumption due to the loss component of the capacitors can increase to the point that heat generation by the capacitors cannot be ignored. Therefore, the temperature rise of capacitors must be suppressed to the range that does not affect the capacitor reliability. An ideal capacitor has only a capacitance component, but an actual capacitor also has an electrode resistance component, dielectric loss, and an electrode inductance component