It depends on how much you give them and you estimate the treats for them in a week. For as long as it is tightly sealed so that it will not receive any fungus and bacteria that can cause bad effect.
Nuts are definitely not good for chinchillas because it can cause fatty to their liver. When it comes to wood any wood collected to use for chewing should be absolutely pesticide-free, and not treated, glued or painted. Collected wood should also be soaked in hot water, then dried. You can also...
I am glad that you have shared your vet experience and you recommended an expert vet here in this place and we don't need to worry for this matter. I would love to see their services and will check if they can do a home service such as grooming.