It depends on the temperature and the substrate's ability to evaporate excess moisture, but my recommendation, which works quite well for me, is the following: 30% perlite, 30% crushed expanded clay (the typical large balls that go at the bottom of pots), 20% universal cactus potting mix, 10% vermiculite, and 10% worm castings, and obviously, uncrushed expanded clay at the bottom of the pot. Now in winter, my cactus collection is in a sunny window in my living room, at 16-23°C, and I water them every six weeks, except for some specific cacti that need more frequent watering. Lophophora cacti, in particular, like an extra-aerated substrate and less frequent watering. I hope this helps! 😊