i think this is one of those questions that is very interesting to find an answer to but doesn't effect us to any great amount.
I understand about the bacteria etc & what it does but everything i do against "the facts of bacteria" never does any harm to my fish at all.
Every 4 to 6 weeks i unplug the filters & empty/clean/flush them completely including piping at the same time i do a 40% water change, hook it all back up & get it running again. In theory i have killed all bacteria that i had & now my tank should totally or partly re-cycle to build up the bacteria again.
I have around 30 africans in a 200L tank so stocking is high & never had an issue in almost 3 years. I used to worry about it but really don't see the need to anymore, there are more imprtant things to worry about than how much the bacteria is effected if the power goes off or if i do a complete clean of the filters.
a few weeks ago we lost power for 12 hours or so, the only thing that happened was the temp dropped a few degrees, the power came back on & there was no problem at all.