How often to apply wax,to cabinet?

Wax, once applied, doesn't go anywhere unless removed by friction or abrasion. No need to reapply as far as the protective aspects go unless you're rubbing it off somehow. I would not agree that wax is the ideal panacea for wood care. Veneers can dry out and delaminate. I have been of the opinion that keeping room humidity levels high enough is more important than any waxes or oils. If wood veneer becomes dry, an oil purpose made for remoisturing wood is a good option.

Gammajo, any finish that will protect wood from water damage isn't going allow moisturizing oil to get into the finish either. Naturally oily woods like teak that have an oil finish do benefit from occasional moisturizing with oil I think. But most hardwoods don't have much, if any, natural oils that need replacing. After thinking about this, I imagine pretty much all speakers are manufactured in plants that use a catalyzed urethane or acrylic lacquer finish. If this is the case, the wood is sealed and waxes are only going to protect against abrasion and help to keep dust from adhering to the finish. Again, the best protection for good wood is to avoid large humidity fluctuations and air that's too dry.