Paul,
I can’t speak to TKR specifically, but I have both knees operated on (for torn lateral meniscus), and I will eventually have to have TKR bilaterally so I have given this a fair amount of thought. I’ll add my experience and thoughts, fwiw.
I had my knees operated on separately and it’s a good thing that I did because I had significant complications both times - protracted patella tendonitis to be exact - which made recovery far longer, years rather than weeks in fact. Had I done both knees at the same time, I would have been screwed from a quality of life perspective because due to the patella tendonitis I was unable to regain strength and muscle mass for years after each surgery. This was when I was in my mid- 20’s and very athletic, which I still am thankfully. But the upshot is that I was hobbled on one side for several years after each surgery, and I would have been totally screwed had I done the procedure bilaterally.
Of course my case was unusual and looking back over the years there has been evidence that I do have a over active inflammatory response. Still TKR, as you know, is a very rough surgery, and if recovery doesn’t go as planned, for whatever reason, having both knees out of commission for a protracted period of time could be a real physical/mental/emotional bummer.
Also, having had multiple surgeries for various things, I find that my body likes the effects of anesthesia less and less every time. I couldn’t urinate for 3 days after my last surgery a couple of years ago, so personally I’d rather spend as little time under as possible during each surgery.
Finally, I found Physical therapy a bitch. I mean rehabbing knees, at least 20 years ago, was very painful. I saw lots of people literally crying as the physical therapists manually worked their legs to get the range of motion back. Honestly, I can’t imagine having to rehab both knees at once, only so much pain one can tolerate at a time. Things may have improved in that sense in recent years, perhaps I was just too stubborn at the time to take my vicodin, I don’t recall 
My current thoughts are that I’ll do one knee at a time when it comes time to do my TKR’s. That could change, and certainly the allure of getting it over and done with all at once is strong. The fact that your wife has you for support, both physically and emotionally, does make for a stronger case for going the bilateral route - I was, and still am single, so having to rely solely on myself after surgery like this does color my thoughts on the matter rather heavily.
Hmmm, guess all of that probably wasn’t too helpful Paul, but maybe something in there will be useful. Either way, I’m sure your wife will be fine in the long run: Most people I’ve run across who have had TKR said they were glad they did it and they were eventually pain free or at least had much less pain after recovery than they did before having the surgery.
BTW, you might want to ping David Levine on this, I know he had TKR in recent years and you know he won’t candy coat his thoughts on the experience 
Loren