Your Apple Watch doesn't need constant maintenance, but reboots can help in some circumstances. With most gadgets, it's an accepted rule that you should periodically restart them for the best performance. A reboot doesn't usually hurt apart from the temporary downtime. That downtime might matter in some cases, particularly when it comes to wearables like the Apple Watch.
Apple's watch OS is a complete operating system, running various apps and processes in much the same way as an iPhone or iPad. There's the potential for processes to become 'stuck' or otherwise glitch out, in which case a restart will give them a fresh slate. Meanwhile, if caches aren't periodically flushed, they can become so bloated that they eat into room needed for other functions.
Apple specifically suggests restarting your Apple Watch if it doesn't have enough room for an update. All that said, watch OS is also lightweight by design. In practice, then, Apple seems to have built watch OS to keep its own house in order. The reboots associated with installing new versions of watch OS appear to be enough to keep everything running smoothly.
If you're noticing bugs, freezes or unexpected slowdowns, a restart should be your first troubleshooting step. Apple doesn't have any official guidance on this point. Our verdict is that when you're experiencing relatively smooth sailing, you don't need to worry about preventative Apple Watch reboots. Apple's software is engineered to run nonstop, no matter which watch model you own.
Source: Engadget · Summarized by HeadlinesBriefing