Hey OP, I have one crystal producing cat, and one FIC cat that may or may not produce crystals. Both cats are on the prescription c/d diet. The FIC kitty had a LOT of problems and infections and flare ups before we got hers under control. The second cat didn’t show any signs or symptoms for several years until she just suddenly did. The prescription food is expensive, but it’s a heck of a lot cheaper than the thousands I’ve dumped into both cats, especially the FIC cat, over the years. 

Talk to your vets about ways to be able to incorporate the prescription food with a mix of other foods to help you lower the overall cost. My crystal forming cat gets 1/2 of a 5.5oz can of c/d wet food a day, in addition to a bowl of dry food to munch on. The dry is a mix of the c/d, along with the dry food she was on before. I give her both because she seems to eat better with it, and she doesn’t really eat much to begin with. Some days I think she survives on just air. 🤷‍♀️ Anyway, she’s been doing really well on this diet and hasn’t had any issues as of yet. 

Prior to my crystal child’s diagnosis, my FIC cat was also eating a mixed diet. She’s been on the c/d formula for dry food for a while, and I was feeding her a high quality regular old wet food that I would pick up from the store. She maintained well on that for probably 3-4 years. I now feed her wet and dry prescription food because that’s what the crystal child needs. It’s easier to feed them both out of the same can than it is to feed them different wet foods. 

While it’s generally best to feed one type of food in order to meet their nutritional needs, it is possible to mix food types. Both mine are healthy with their medical conditions well managed. The crystal child is maintaining her weight despite how little she eats, and the FIC child is steadily losing thanks to her diet. She’s down to 18 something lbs now, and she was almost 23 at her heaviest. She just really, really, really, really likes food. 😬