Depends on how lazy I'm being. I'm growing in DWC, so in a perfect world, I'm keeping two large totes with air stones, one with a full strength nutrient solution and one with just water, depending on what I need to top up with and provide an emergency rez change if anything looks off. It's basically the same amount of work as doing it without a spare rez, just lets you clump it up more so most trips to the garden are quick, but you do have the longer days eventually.