Winterizing black and gray tanks

Hi Folks. 'Been RVing for a dozen years in the freezing north, and never really worried about this, or seen anything written or found searching. Do you think the black and gray should be completely drained, or tank chemicals in as usual (plus whatever antifreeze gets in there from adding to P-traps)? Do you think it's good for the O-rings to dry out over winter if empty? I have done both. Have not had ever the outlet pipes freeze or break, but have had them start leaking, and replacing them was not a fun job. Would rather not have to do that again. Any advice appreciated. Thnx. -Luther
2017 Flagstaff Microlite
2009 Cherokee 5er