I thing you should some optimization's for this scenes.
From my experience amount of noise in interior's area's very depend's on window glasses and curtains material.
Need to be sure that windows glasses do not interfere to light passes from environment through the glass from HDRI or Corona Sky.
May be need to use Corona RaySwitch mat for turning off visibility of glasses for Indirect illumination, using thin glass option in Corona mat, using additional fake Corona lights with occlude
other lights option turn off -- on windows, which greatly speeds up the noise removal process and simplifies lighting setup, or portals /although I personally have never felt a particular difference in speed with or without portals:)))
And don't use max Hair and Fur on carpet's and refraction on plant's leaves:))Same problem with refraction may be on curtains material with using textile textures in refraction slot/
Also Corona Layered material itself ,+ and using AO map as mask in some cases /On large areas--etc. floors,ceiling,walls,/ may cause much longer render//
Good luck:)
PS. material of curtains need some more attention/