I don't waste crystals on mod refreshes. Much easier to just wait and see what comes up. If there's a good one and i have enough credits that aren't better spent elsewhere i buy it. Crystals are better spent elsewhere. You only get so may credits a week anyway. In the long scheme of things getting your mods the day of a credit heist or a few days later won't change anything. And not wasting hundreds of crystals on refreshes and getting gear or shards you neeed instead will help yoy more. If you save credits for them you'll still get them. And you can always use the crystals for cantina refreshes to farm mods. At least then you get credits and cantina currency if you come up empty and if you get a good one you don't waste 3 mil credits on it. And if they are all shitty sell them for credits and you basically farmed credits which are always needed.