But I think the deposited coins to the mixer going to be delivered to another mixer user later, at least it is the way most coin mixers work. So if you cannot recover these coins from coin mixer anymore, why not send them to some address, wait longer, and then you could use the coins as everybody expect the coins come from the mixer to somebody else?
This isn't how it works. If they just keep the coins and then spend them without mixing etcetera then they will be traceable. It's not a question of what people "expect." If they are mixed correctly and at a mixer who co-operates and doesn't sell them out, then no one will be able to follow where those coins end up. You can't just not be secure because "people won't expect it." I won't leave the front door to my house unlocked because people will expect it to be locked, do I? That's security through obscurity which is a poor ideal to follow.
