I don't find that mine produce urates every day, I'd say each tort produces urates probably at least once a week, but it does vary.

I've had the gritty urates once, its easy to spot as the urates are lumpy and, well, gritty. It went away when I provided more baths.

An absence of urates could mean dehydration though, as they might be too dry and lumpy to pass out of the torts system.