This depends on many factors. The following details have to be taken into account when giving an estimated time of delivery. First off, is how much research has to be done to achieve the results. Next, the scale and level of detail required in the model and what the subject of the model is. If there are any special requirements such as working features, lighting and other electronics. If parts are already available for the model from either DMG sources of from other companies. There are many other items to look at when estimating the number of man-hours that go into a model. Generally a model may take anywhere between a week for a simple model or up to 12 months for some of the more detailed and sophisticated models.