Great question! I have used these in the past and they do work really well to help develop bow technique. I find that some students really struggle to place their bow hand in certain spots and these tools can really help. I suggest using the tools for up to 1 year, and try to not use it past that. Sometimes I’ve only used these tools for 1-2 months with students, and find that they are ready to take them off. The indicator would be to see how they hold the bow without the tools.