[Kars]

I think your second one is much better because your body remembers and reconises the situation, therefor kick in the energy preserving reflexes much quicker.

I only use some warmup's to turn these reflexes on, like the vains narrowing in your arms and legs.
And they useually come one much sooner than any uncomfort feeling. This safes me a lot of energy for the official attempt.
10' minute breathup? I do only 2'-3' . But I do meditate 5-30 min in advance to find my peace and prepair my body.

Good luck with the exploration.

Carlos