Pokémon Sleep will undergo maintenance from 11:30 p.m. PDT Sept. 8 to 4 a.m. PDT Sept. 9 for the release of Version 3.8.0, which prepares the sleep-tracking game for the upcoming Unexplored Realm Research! Pursue Mewtwo event. The update will slightly reduce the chances of non-Legendary Pokémon becoming full, while the New Moon Day bonus that makes Pokémon less likely to become full during the first snack time will also apply to Legendary Pokémon during their debut events. Version 3.8.0 will also increase the General Store’s Ultra Biscuit exchange limit from three to five and raise the maximum number of incense that can be set up from two to three, although the same type of incense cannot be used simultaneously and incense can still attract only one Pokémon species at a time. Pokémon Sleep is also preparing a future winter update featuring friendship-point rewards, including Main Skill Seeds for continued play, with players set to receive items based on friendship points earned during sleep research from Sept. 14 at 4 a.m. until that feature launches. Players who want to track sleep during the Version 3.8.0 maintenance should avoid updating the app and instead begin tracking from the Under Maintenance screen, as updating during maintenance before starting sleep tracking may prevent tracking from starting properly.
Source: Official Pokémon Sleep news and PokemonSleep.net