So, I decided to go for it and try the 30hr+ process to Rubaud's 3-stage levain loaf. I followed the recipe(s) from Shiao-Ping and David Snyder (via MC's interview with the master).
I will say that I am entirely satisfied with this bread. It's dreamy. The crust is nice and crisp. The crumb is airy, soft, has a creamy aftertaste, and nice whole grain notes to it. The process, however, is a bit excessive and not entirely sustainable on a regular basis.
I started my first build at 6am on Saturday, went for ~10 hours, started the second at 4pm, then the third at midnight. Was up again at 7am Sunday to prep and autolyse the flour and had the levain integrated by 8am for bulk fermentation. I did 5 rounds of s&f in the bowl every 30 mins, then did two rounds of s&f (letter style) every 45 minutes, ending with a 45 minute rest before pre-shaping.
Since the dough has such a high hydration level (~80%), I did not knead it at all. Only s&f's in the bowl or on the table and I was very pleased at the end with the texture of the dough. It was so soft and light, bubbly even.
Afterwards, I pre-shaped into boules, did a bench rest for 15 mins, then final shaping. Finally, both boules went into 450F oven on a stone with steam (via towel method) for 40 minutes.
I would absolutely make this again, but probably follow David's second attempt with one stage levain. That way, levain build is night before and bake.
All said and done, I started at 6am Saturday, and these loaves came out of the oven at 1:25p Sunday. But, that is certainly not a complaint. The process was exhausting but stimulating at the same time. I feel like this bake has stepped up my game. Can't wait for the next.