smart router user configurable performance cache timing

user configurable max time to re-eval queries ( currently, 2,3,5,10,20)

As a user i want more control over the duration of the performance timing cache of my canonical queries in smartrouter. I may be testing and want no cache, or small 1 minute cache. or in production with predicable results and want an extremely long cache like 4 hours. a gradient curve still makes sense knowing the target end timing.