Well the cleaner worked well. I would recommend it... But, as you are thinking, I'm not sure it is always necessary. I wanted to do it to mine to kind of get me back to square one. Then in a year, when the stuff supposedly will wear off... I will hope it continues to not smell... And I assume that is what will occur... My evaporator didn't get like that over night, so I should be good for a while.
Is there supposed to be (I don't think there is) another screen covering the air inlet outside, up under the cowl screen? It seems it would help if there was something else to help keep debris out.
And I sprayed some Lysol inside, on the things that open when you turn the A/C system on.
I think I managed to beat back the D-Stank! WOOOHOOO!