I give my houseplants a shower at least twice per year. This helps prevent pest problems by cleaning the leaves of dust, providing some humidity, and rinsing off any pests that may have shown up. When possible use barely warm water. Be sure to spray the entire plant and spray off the undersides of the leaves.
While my plants are outdoors for the summer is a perfect opportunity to give them a shower.
Before I bring my plants inside for the winter I repot or add compost or potting soil if necessary, spray with horticultural oil or neem oil, and spray them off with a hose.
The oil sprays suffocate any pests that may try to hitchhike indoors.
Mid winter I may carry my plants into the shower and spray them off. If I notice any pest problems I spray them off with horticultural oil or insecticidal soap before showering them.
I always shower plants which are new to me.