Hair dye advice!

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How often is it ok to use 10 vol developer? Would every three weeks be ok?

My hair is in decent condition and I use it with a salon/professional dye to deposit/tone.

My hair is in pretty good condition.

Advice??
 
Where are you using it - just on the roots, or all over?

If just on the roots it should be okay, but if all over it's too much.
 
I dye my roots only every 3 weeks using 20 vol peroxide and my hair is in great condition