As stated, for an overwater leg, 45 minutes is not adequate, basic crew.

But to more seriously answer your question, since the "Integration," the 777 flight manual has changed dramatically. The FO essentially does everything now. His time is the limiting factor. Complete overhead preflight, FMC, Plot the chart, HF's, verify way points, all the ACARS, checklist resets, and the walk around.

I test the radar, and O2. Oh, and do some of that Capt networking. And.....777A's are routinely weight restricted, so that means I'm fighting with zone and load planning to get that last 5k lb weight instead of saving it for some mysterious reason and keeping 20 people off the plane.

Then, that 777 walk around takes like.....30 minutes to walk that far. It's a big ass plane....

The question you should really be asking is, why is the guppy preflight so short? To honestly do everything, my set up takes 22 min. It has for years. It's all the other Capt stuff that goes along with it...honestly go through the flight papers, and not just scroll through. Read the notams. Often Dispatch misses stuff. It really does take that long, and it should you too. If we are doing everything SOP requires.

And yes, I have around 5k hours in guppies.