What type of storage for winter will govern watering practice during winter.If covered with top dressing like orchid spahgnum in still,non moving air in a shed or something I would say if top dressing is moist ,so is soil.
But if outdoors in moving air I would water when needed , like when you not sensing a cooling moist shade for the roots in the soil bonsai soil,just before that time..
So really depends on air movement if you can gauge by the looks of your top dressing.
If unsure,bamboo skewers work really good at measuring the moist shade of the rootzone.Leave it in the soil after watering and see if the bamboo still has cool damp color to it when you think its time to water again.....not neccessrily wet.
I still use them in certain situations.
Open bonsai soil is good!