In Week dimension you can create dynamic rollups so that the content of an item is always up to date.
For example you could create a rollup consisting on 8 previous weeks and use this in reporting. However, in order to keep this up to date you need to add and remove weeks manually as time passes.
You can automate this process by creating dynamic rollups. You can predefine the week ranges and system keeps them automatically up to date. In this way you can set the context in your favourite dashboard to dynamic rollup, and the data is correct every time you open the view since the last context value is saved.
To set up dynamic rollups go to Settings->System and enter values to the setting field.
Create automatic period rollups (enter weeks eg -12,-4,4,12)
You can enter list of number separated by commas to define the rollup weeks.
0 - current week
1 - next week
-1 - previous week
-4 - four previous weeks
So in order to have rollups as in the above example you would enter the following: 0,-1,-4,-12-52,8.
New elements in Week dimension will be created with id-s shift_<value> e.g. shift_-1 (for last week). Since these are non-system elements you can remove them manually. When doing so also make sure you remove them from the above setting or they will be recreated.