We have dry food available at all times (free feed) and give wet food a few times per month. Ariel did get a urinary stone and is now on a prescription dry food (Royal Canin SO), which for the stones she's been great on. Unfortunately it has corn in it and she's allergic to corn, so we have to treat that occasionally (no water cat bath actually works for help her allergies). (She's also allergic to dust). The dry food we feed is Nature's Variety Instinct. It's a high quality food that you have to go to pet specialty type stores to get. PetsMart, Petco, grocery stores, ect will not sell it. We dry two hours every so often to buy/stock up on it and then keep it in air tight containers. Here's a link to their website if it's something you might be interested in:
http://www.naturesvariety.com/
We also get their wet food as all three of my cats actually like it. (I have one that won't eat most wet foods, but loves theirs.)