Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

How to determine duration of a common stock whose dividends grow in perpetuity?
The Dividend Discount Model is based on the concept that the present value of a stock is the sum of all future dividends, discounted back to the present. Since you said: dividends are expected to grow at a constant rate in perpetuity ... the Gordon Growth Model is a simple variant of the DDM, tailored for a firm in "steady state" mode, with dividends growing at a rate that can be sustained forever. Consider McCormick (MKC), who's last dividend was 31 cents, or $1.24 annualized. The dividend has been growing just a little over 7% annually. Let's use a discount, or hurdle rate of 10%. MKC closed today at $50.32, for what it's worth. The model is extremely sensitive to inputs. As g approaches r, the stock price rises to infinity. If g > r, stock goes negative. Be conservative with 'g' -- it must be sustainable forever.  The next step up in complexity is the two-stage DDM, where the company is expected to grow at a higher, unsustainable rate in the early years (stage 1), and then settling down to the terminal rate for stage 2. Stage 1 is the present value of dividends during the high growth period. Stage 2 is the Gordon Model, starting at the end of stage 1, and discounting back to the present. Consider Abbott Labs (ABT). The current annual dividend is $1.92, the current dividend growth rate is 12%, and let's say that continues for ten years (n), after which point the growth rate is 5% in perpetuity. Again, the discount rate is 10%. Stage 1 is calculated as follows: Stage 2 is GGM, using not today's dividend, but the 11th year's dividend, since stage 1 covered the first ten years. 'gn' is the terminal growth, 5% in our case. then... The value of the stock today is 21.22 + 51.50 = 72.72 ABT closed today at $56.72, for what it's worth.