From time to time we'll publish an image of a bare PCB with a thermal camera. We don't do this in every review, mainly just when new SSD controller comes to market. To show the range of heat generated, we publish two images: one with the drive at idle for 10 minutes and another after writing 4KB blocks for 10 minutes.
In some environments, you might not want a solid-state drive that hits 114 °C under heavy load.
NAND flash operates best within a certain temperature range. It's still capable of accepting writes at the upper end of that spectrum, but endurance suffers. Even operating flash at high temperatures can cause issues with long-term reliability. NAND consumes power, so it does generate a small amount of heat. But most of an SSD's thermal energy comes from the controller. We look at the design to see if the manufacturer places the flash far enough away from its processor.