This is just my personal experience. I have nothing scientific to back it up--so take it with a grain of salt. I have been using Renavive for about 8 months on my stone pig, Marty. He had surgery to remove a bladder stone in October 2016 (at age 2) and a second in March 2017. Despite being put on a low calcium diet immediately after the first surgery, he developed the second stone only a few months later. The second one also grew much more quickly than the first one. We started him on Renavive as a preventative measure as soon as he was given the all-clear after the second surgery, and we haven't seen any signs of stones. (Big knock on wood here!)
This is just what I've been doing based on anecdotal evidence found here and other places. Typically, I go through cycles with it. Once a month, I'll give it once a day for a week to sort of flush his system. The rest of the time, I give it roughly 2-3 times a week. For dosage, I sprinkle a small amount of the powder--kind of the amount you could scoop up with just the tip of a 10 cc syringe. I then add a splash of some kind of 100% fruit juice to help counter the potent smell of the Renavive, and add enough water to make roughly 10ccs. Our vet recommends extra fluids to prevent bladder stones, so I try to give him as more water. Marty has no problem taking that amount, but you could add less water and just have a more concentrated solution.
Whether it's truly the Renavive, or we've just gotten lucky, I really couldn't say. I will say that he leaves more powdery deposits around the cage when he pees than he did before he ever formed the stones. I have no idea if this is good or bad--but since he's on a low calcium diet, I've kind of been thinking along the lines of "better out than in."