I have determined the median survival time using Kaplan Meyer and identified also the customer retention percentage. Assuming that CLV = [M-R]*[(1+d)/(1+d-r)], where M is the customer revenue during a year, R expenses in the customer retention for year, r the retention rate during a year and d discount rate for a year. I have assumed a discount rate of 10%. The business assumes a contractual setting, where the customers have a contract of a year.

Is this approach correct to calculate the customer CLV? I have also some dificulties identifying the correct discount rate and how to get a correct value?