Sending them in sooner would be beneficial. That being said, I recieved interview invites from almost every school without having all the letters in so it's possile.Would send them in asap.
Some schools may put your app on review until they recieve LORs.
Some may give you an ii before you even send out LORs then ask you to send them afterwards.
Would send them in so you max your chances and leave no room for doubt.