I am playing a level 8 Incanter from Spheres of Power. As a full caster, this gives me a caster level of 8. I have a trait which increases my caster level for the destruction sphere by 1, and I have a stave of destruction (+1). This gives me a total CL of 10 in destruction. This has allowed me to qualify for the Wand Wielder feat, which requires a CL of 10 or higher.
Am I only allowed to use the feat when I'm wielding the staff (so I would be wielding both a stave and wand to benefit at the moment), or am I just allowed to have the stave on me?