As with most marketing and sales questions, there is a short and long answer to this question. The short answer is: as many times as it takes. The longer answer isn’t quite so black and white.
Let’s start with exploring why someone would ask this question in the first place. What I’ve found in my many years, working with companies of all shapes and sizes, is that there is a natural inclination to treat inbound (or website or marketing) leads very differently than prospects identified and cultivated by individual salespeople. This is especially true for those industries that still rely heavily on cold calling.