That is fairly frequent. Typically a BP will expel urates once every 1 to 3 weeks. Are there any other signs or symptoms of problems? Is he/she eating normally? Are their behavioral differences since he/she started urinating frequently?

If it is a major concern for you, the best thing you could do is see a vet. Nobody here is going to be able to diagnose a problem, so if YOU feel this is abnormal enough to see a vet, than you should.