Mi Box (Oreo): ~56 days ( https://postimg.cc/4mFsdSFZ )

Shield TV 2017 (Pie): ~58 days ( https://postimg.cc/1V31RGGf )

Both boxes are fairly stable lately without any noticeable slowdown. Both are loaded with many apps & games with adoptable storage and used regularly for video streaming and some gaming (Mi Box is mostly limited to 2D games and emulators). Mi Box used to have occasional wakeup issue due to losing pairing with remote. But with Wakelock fix, I am always able to wake it up now with casting from phone. Shield TV used to experience rare auto-reboot once every few weeks when adoptable storage is unmounted. This hasn't happened since the Android Pie update.

Please share your experience, preferably with screenshot.