Most repeater controllers these days have a settable hang time where the carrier stays open for a few seconds after the last transmission. And many have a courtesy beep so you can be sure the other station is done. Sometimes, when there is a linking situation (like CoConn) you can here each relay repeater drop off with a unique courtesy beep. That gap at the end, before the beep, is squelch tail.
Some repeaters have none at all so you hear stations cherchunking to hear themselves drop (self service radio check) but it never happens.