Does pictures shared in Shared Photostream either by me or others gets deleted by Apple like Photostream after it reaches certain amount of pictures or over i.e. 30 days?

I understand if I share pictures or album with Shared Photostream, then only me can add and delete the pictures or album from Shared Photostream. What I don't understand is whether the pictures or album shared are limited as per Photostream itself in this case 1000 pictures or 30 days old... Which ever comes first. Apple says that shared photos does not count towards my iCloud storage but it doesn't explain if these pictures are limited and/or save onto the iPhone/iPad etc or in the cloud. Or they simply remain active until (If I was the one sharing the albums or pictures) I delete them in which case will also be deleted from everyone else's iOS/Mac etc devices...?