Personally, I am on the side of - it depends.
I have had main characters die. In volume 2 of my Matchmaker set Lois died of old age, in her 90's. That was used as the setup for Clark to be moved forward in time by Herb to meet her next incarnation, Lorelei.
In Volume 4 Lois, actually Alt Lois, who we all were led to believe in canon had died in the Congo. In volume 3 I had her saved by Alt Clark, but like Schrodinger's cat there are 2 possible outcomes, when she survived it was because a new reality had been created. In volume 5 I had another Alt Clark die after Lois had been changed into UW so that Alt Clark and she could get together thanks to Herb.
I did put a disclaimer before the chapter involving the death of Lois as a warning even though it was old age that was the cause. Since it was a plot device and not the object of the fic I kinda glossed over it. When Alt Clark lost Alt Lois that became a major issue for him, but here again it was a plot device setting up the union with yet another Alt Lois.
As I said above - I think it depends on a number of factors. I have been having a hard time with your current story, Terry because it is like the death of Lois is the central issue. It does engender a feeling of unease because this is a character that we, as a community, have a lot of emotion invested in.
Admittedly I was treading on quicksand when I was writing the stories listed above. I justified it to myself by saying - these are alternate universe versions of the character, not canon and therefore expendable if it will move the story to the desired conclusion.
I have started doing the same thing with your fic. These are obviously not the canon characters because this is not how it went. In canon Lois is okay and forever will be.
