Firing highs and lows

It was a bit of a shock to find the kiln had still not reached temperature when I went to open it on Sunday morning.  As this was such an anomaly for a kiln that is usually so reliable I had anticipated a firing disaster.  Thankfully the results were some of the best we've had!  Not sure how I go about replicating though......

The down side is that I have to repair the elements in the kiln - any advice/assistance gratefully accepted!