Lots of opinions around here on that question. Many fail to account for significant differences in sport history. What was best for me 30 years ago is not best for me today. I am a different (unfortunately, weaker and slower) athlete today... but I have years of developing an aerobic system. My personality (some would say dedication and focus) does not permit me to sit on a trainer for hours on end over the winter. As I age, I need to maintain my strength and speed. I choose intervals over long steady. My sport experience allows me to add endurance pretty quickly once the weather improves. I'm a strong swimmer, so I use lots of winter pool time to maintain aerobic conditioning. As an older athlete, I need to spend my hours in the gym over the winter as well. All that said, if I want to reach elite levels, I will need to include as much aerobic time as recovery permits. That's where my life stressors come into the equation. I just finished volunteered to work the hardest shifts in Dec-Feb. That lowers my stress next spring when the real training comes. Good luck with your personal puzzle... that's why I've been having fun as a triathlete for 35 years, and probably explains the fact that I've never been to Kona ;-)

...probably also important to note that I have ALWAYS incorporated an Oct-Mar "Barry P" (frequent easy volume) running approach, and gave up open marathons 20 years ago.

I did Kona back in 2003 through an Australian "winter". Where i live in Western Australia the overnight temps can be relatively cold but still moderate daytime temps. My training was the same as any other IM, if anything I was doing more volume as I was going to Kona. Due to the weather I missed a few more sessions. My usual plan was to do most of the distance work 16-6 weeks out then shift into speed work 6-7 weeks out to sharpen up. Unfortunately I remember getting the flu 6 weeks out and basically missing 3 weeks of speed work which was leading into my taper. But anyway, if I was to do it again I would follow a similar plan, get in the long distance then wind the volume back and increase the intensity before tapering.