The life-time value (LTV) of a member is the total amount of revenue generated by them throughout their time on your dating site. Some will continue to re-bill for many months, therefore LTV is best generated in the longer-term from a larger data set
It is important to consider the life-time value of a site's member pool when calculating how much you can spend on acquiring members for that site. Some sites have higher LTV's that others, so it is important to look at these on a site by site basis.
When calculating LTV for members that are still currently using a site, it is difficult to put a definitive figure on this as we don't know how long they are planning on staying for, therefore, in this situation LTV is a prediction of the revenue attributed to the members based on an average of data from previous members.