In normal river drifting situations that will be more than you will ever use. Really if you need more than 1/2 of that you should not be anchoring in that spot.
I use about that. Better to not need it than not have it. I have used the extra length to line the boat a few times. Also handy to have if you go to a lake. Only down side is the extra length can get in the way at times. I don't use a floor pulley and just keep the rope in a milk crate.
