How frequently you need to fly varies greatly. I've been a passenger in our group plane with pilots who fly less than once a month, but who appear to keep their skills. I've flown 24 hours since Jan1. This is less than I hoped for, due to weather. I quickly lose my skills if I do not fly. Fortunately, I lose my confidence slightly quicker than I lose my skills. Only when very current will I be happy with gusty crosswinds.