We have used a bell ever since my son got his GSP, and it has proved VERY good!
However, the last few years we have been using a collar with a locator mode , because if we can't hear the bell we know he is on point, but just where in the cat tails or heavy bush ??!!
It has been invaluable and has been the direct result of taking birds where without it we would have not had the opportunity.
We only use it when we can't here the bell, then give it a shot and the collar will sound, letting us know where Louie is!!
I love the bell however, we got ours from cabellas, and one also from Ugly dog.com.
They tend to get torn off, lost, etc, so we always have a spare!!
DT