CJB1 Auto Generation of Settlement Rules

I have created a setttlement strategy for the auto generation of settlement rules, based on the WBS element resposible cost center.

This works as expected and the settlement rules are correctly generated.

However,

Let say I run settlement in period 9. The settlement rule now displays first used and last used periods of period 9 2009.

If I run CJB1 again in period 10, a new settlement rule is created for the same cost center (responsible cost center has not changed), with a validity date from period 10.2009.

We were planning to run CJB1 for all projects every month prior to settlement as a catch all just to make sure that all WBS element settlement rules have been created.

If we follow this process a new settlement rule, for the same Cost Center is created each month, with a new validity from date.

Whilst this is not a problem, and settlement will occur as expected, we will have many settlement rule lines for the WBS element for the same cost center over time.

My question:

Is this the correct behaviour, and if so is it possible to only create a new settlement rule when the responsilbe cost center is changed?

Thanks in advance.