Deadline to apply for FLR spouse extension

Hello,
As I understood it, we are able to apply anytime before the current visa expires, has anyone experienced doing this within a few days of visa expiry?
Also since we were granted initial FLR, the rules seem to have changed, can anyone tell me if after we apply online, scan documents, that we have to attend an appointment in person as well?
Also does anyone know how late documents can be submitted i.e. do they have to be uploaded on the same day as the online application or is anything accepted as long as it's uploaded before this appointment at the Visa centre?
Thanks~