The question here is: what is the result of fireAllRules()? Caching the result of this method is trivial: it's just a number! I think that what you need to build is your own ad-hoc cache that knows how to extract a 'result' out of the session an keep it handy. Implementing this mechanism shouldn't be that hard (at least for simple - no nested- Facts) and once you have it you can validate the benefits.