Concerned about temps

[Weatherby]

Tonight while playing World of Illusion, I began to notice some black lines flickering through the game's image, which at times caused the image to freeze and catch up a few seconds later. I've never experienced this before on my pi, which I have had since Feb 2018. I've occasionally gotten a heat warning, though that was always on PSX games, and generally I am able to play PSX games fine for extended periods without a warning or any throttling. Generally speaking, I am not anal about checking my system's temps.

This is my current case, with three heat sinks applied with the included tape, two on the top, one on the bottom: https://www.amazon.com/gp/product/B00ME5XUAG/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

• Using a Pi 3 model B board.

• VRAM in ES is set at 80, I'm not sure if this matters.

• Current theme is lilbud's Switch Dark theme, set to video for the gamelist, OMX player set to on, video screensaver also on.

• Idle temps on this set up show around 63-65C (checking while running Carbon, the temps are consistent there too.) While idling in World of Illusion I'm seeing it consistent with these temps. I let my pi idle for a bit on Silent Hill, which returned a temp of 70C.

Part of what is prompting my concern other than that unusual performance is that the metal near the stereo output port is discolored, it looks like some small brown splotches as though it was burned. I am not sure when they first appeared there, I only noticed recently when cleaning the shelf my pi is on.

From looking around, it seems most people have lower idle temps than me, and I know the Pi3 is meant to throttle around 85C. I'd like to avoid being in a situation where I need to buy a new pi3 board, since I'm holding out for a 4 when Retropie has a build ready, so i want to see if these operating temperatures are cause for concern?