One thing that you need to keep in mind -- if you back-off from CDN loading to loading a local copy, you'll almost never be testing that scenario so be careful

One thing that you need to keep in mind -- if you back-off from CDN loading to loading a local copy, you'll almost never be testing that scenario so be careful that a massive influx of local requests in a CDN-is-down scenario doesn't melt things. It brings up a broader topic of reliability testing.. every one of these branches inserted into the code creates another point at which performance/load metrics change. Testing all the various combinations can be difficult.