I think the conversation between AJ and BB was headed in the right direction. In my experience a normal training regime of less than 100 miles a week with a metric century thrown in every few weeks is all one needs to be century ready. However that does not guarantee success, I also think that you would have needed to be experienced in riding a century as well, you need to know how to pace yourself, hydrate and refuel. It is combination of things that will allow you to be century reading with a minimum of physical preparation. In the OPs case, I would think he could be century ready in short order matching his pace with his conditioning - not expecting a less than 5 hr time right out of the shoot. Others might try with a fast start and blow up well before the end, then have a miserable finish struggling in at a very slow pace.