A well-presented DCF analysis may convey a strong sense of certainty, but always remember that a DCF is built upon several key assumptions that can drive large variations in project / firm value when different assumptions are applied. These include: 1) Terminal value (for firm valuation) 2) Revenue growth assumptions 3) Operating expense ratios 4) Size of initial and periodic capital investments 5) Discount rate (cost of capital/required rate of return) To avoid a numbers quagmire, focus on these assumptions and how they impact the valuation. If you have time and access to the model, test ranges to come up with a reasonable range of valuations or best/worst case valuations.