I stayed in windowless hotel room in SG before. For about one week plus. Felt totally fine since daytime I was in office, and during that weekend I was out with friends.
Ultra good to sleep in too. Switch off lights and you get total darkness. Easy to sleep until lose track of time though lol.
When I went Taipei, I also stayed in a windowless boutique hotel in ximending. Felt fine too... If want to know the weather, I just step out of room to beo, coz my room same level as reception desk and its ceiling to floor glass windows there.