Large or multiple smart collections can seriously impact performance.
It would be useful to disable a smart collection or, even better, disable a set of smart collections, so they are no longer processed until re-enabled.
As it is we can only delete the smart collections and recreate them when we need them again next month.
A selective export and import option of smart collections would serve a similar purpose and would add functionality to LR but would not be as simple to use just for this disable/enable purpose.
Whilst here I would also like to add my vote to the many people who have asked for a smart collection A only to select images from within smart collection B. Though I can see some concerns: how many levels down does it allow should B only select from smart collection C, etc. That is maybe why they have not implemented it. Also there would be a possibility of creating an infinite loop should smart collection A only select from B but B is set up to only select from A. Perhaps it could be limited to only allow selection from smart collection B provided that B does not have use any sub-selection of its own.