Hello,
I just got a juniper, Bonsai and I don't know when I should wire it. Should I wait till i repot it? its very small right now so I don't know if i should wait or not.
You can wire anythime. just make sure you know why you are wiring. If your plant is very young, it may be best to just wire lightly, and chuck it in the ground for a few years? As always.. Pictures help to asses..
Assuming you mean how often can a branch be bent, not how often can the wire be bent: that depends on the type of tree, the size of the branch, how far you are bending it, how you are bending it, what materials you use and other circumstances.
I will share a picture one sec got to take one 
