Relative Time In A Data Warehouse

At my office, we've been slowly working on putting together a data warehouse.

We're a financial services company and one of the services that we offer is debt collection. As far as reports go, our clients are interested in knowing how much money we collect over time. In particular, they want to know how many payments we've gotten 5, 10, and 15 months (and so on) after we receive a case. (Obviously, the 5-month payments are also included in the 10 and 15-month calculations).

When I wrote this report using our transactional database, I was completely new to SQL and the ever-resourceful Patron Saint took pity on me, so you can see a good description of the details at http://www.sqlteam.com/forums/topic.asp?TOPIC_ID=78510

Now that I'm no longer a total newbie at SQL, and having been through a relatively extensive seminar on data warehousing, I've been entrusted with researching certain aspects of data warehouse development (rest easy, though, folks - the real DWH work is not being done by the very inexperienced me, but by an actual professional :) ).

My question:

how would you model this kind of "relative time" in a data warehouse? How would you display the 5-month, 10-month, and 15-month payments in a DWH? I can't really imagine that the kinds of joins necessary to do this in a transactional database would be desirable in a data warehouse.

We have the following:

1.) FACT_Payment: A fact table showing each each payment to the most detailed granularity. One attribute of this table is the payment date. Another attribute is a foreign key to the case dimension described below.

2.) DIM_Case: A dimension table showing information on each case, including the case start date. DIM_Case

3.) DIM_Date: A date dimension table.

(For added clarification: The FACT_Payment payment date has to be 5, 10, 15 months etc... after the DIM_Case start date.)

Any ideas, comments, experience with something like this?

Thank you.