Thanks for the additional information Christian - I took a look at the PR and added a few comments. I think you can approach this as another quota (number of activations stored per minute or per hour) and setting the quota to 0 would disable all stores.
I also don't like the way this was done in the artifact store - it's a fast hack, but bleeds through the abstractions. We should not do this in my opinion. At the least, the invoker (and controller) wasted effort and held up resources gathering logs etc only to be thrown away later. -r