I don't know if you've read this, but we cover limiting updates in the SaaS and time-limited licensing article.
I need to deactivate and activate again to get the real data.
And if you read the License Features article, you'll see that you don't need to Deactivate & Reactivate to get the latest feature values. Simply call IsGenuine() to see if you need to reactivate. If so just call Activate (no need to call Deactivate).
wyUpdate should automatically check if LimeLM is used and stop updating, if the customer isn't allowed to.
You can actually do this server-side. Simply refusing updates to users without the latest update contract (or however you sell services to your users). We explain such a method in the SaaS and time-limited licensing article.
We also have an example PHP code example in the Web API zip file. Go to your API page to get it.