There should be somebody at the LAN counters with the 4M flight to EZE going at around 8:45pm and the LA flight to SCL around 9:30pm. If you pick up your bags you should hopefully be out by 7pm and they'll still be there. Sometimes the MIA folks aren't open at t-4 but with other flight leaving earlier you should be OK and I haven't seen LAN not check bags a little early for Premium/ Elite passengers. Last short late trip (12:30 am) I took was UIO-MIA and there was a light dinner service and no breakfast. Enjoy Peru.