The Datacolor SpyderX is a breakthrough product, but not for the usual reasons. Instead of creating the absolute best monitor color calibration tool, Datacolor built the Toyota Corolla of colorimeters: an affordable solution that is super simple to use and delivers results that are good enough for most users.
Firefox is a fully color managed browser and since version 89 it applies color management to all untagged images and page elements by default.
The short answer is: it's not necessary to recalibrate a good quality modern monitor as often as most people suggest. But the long answer is: it depends on how your monitor behaves over time and what kind of color accuracy your work requires.
The X-Rite i1Studio Display is an excellent device, either for new users who are looking into getting their monitors calibrated for the first time or seasoned color management nerds. It offers the same sensor as the more expensive i1Display Pro model, but with capped measurement speed and simpler software.
Learn how to get better color accuracy from our existing monitor without spending any money on a monitor calibration tool.