I would say disassemble the notebook and really clean out the fans. If you smoke or have pets, they will plug the fans up in a hurry. The ROG notebooks do not tend to collect tabletop dust since their air intakes are on the top of the computer, not the bottom. That "speaker" grill right under the display is partly speaker grill, and partly air intake. The slots on the bottom panel also take in air, but that is mostly for cooling the RAM and the HDD. The primary CPU/GPU cooling comes from the top of the computer--great work ASUS!
🙂This design tends to reduce the acquisition of ambient dust, but pets release a load of dander, and the tar and smoke from tobacco really sticks to computer fans, I'm told. Those are the only two sources of serious cooling problems that I can think of. The temperature at which your GPU is running at idle is by no means dangerous. Mine sits at idle at 45 C, and runs up to 55 C under load. Those 90 C load temperatures are a cause for concern. The final, and worst alternative is that the thermal interface grease has failed, which requires either return for repair or a
lengthy disassembly of the notebook that voids the warranty.
