Different NumberOfDaysToKeep for different interfaces in the same namespace

Hi community,

I got quite a busy namespace with lots of services, processes and operations. The Ensemble purge that runs daily keeps the last 10 days. I would like to increase the NumberOfDaysToKeep to 60, but only for a small number of the interfaces in the namespace, and I would like to do it in a way that will be seamless to the users, so they will not have to change the URL of their calls, or will even be aware of the change.
The one idea that I had is to move these few interfaces to a new namespace , but how do I then do it without affecting the URL? with a Pass-Through interface somehow?

The other idea is obviously to write custom purge routines for each interface or a group of interfaces, but that is too much of a hassle because it is basically a temporary  thing that we need, and wouldn't like to spend too much time on it.

I would like to hear what you guys think about these ideas as well as if you got any other ideas for me.

Thank you