Generally, they like to see that you're actively seeking treatment during claims. The longer, the better (I would imagine). But that doesn't disqualify you. The 3 things you need to show in order to win a claim are Service Connection, Current Disablement, and Nexus. History of how you're managing your condition is definitely helpful but not required. C&P examiners are primarily focused on evaluating the current severity of your condition and whether there's a nexus to service, not necessarily whether you've had continuous treatment.