Draining bottles are not "absolutely necessary" but they help recovery a lot. any fluid build up is going to take a long time to go away (months), so they try to let it all drain out. I will have to have mine for only two days. surgery was monday and i get them out at post op on wed.
they aren't that big a hassle. i have to empty them a few times a day. so far i have gotten about 3 oz out of my left tit and 1 oz out of my rightIt was really slowed down now however.