The S2 has half the power costs, so will add like 10 weeks lifetime. But not shippinjg before in 3-4 weeks, so make it 6 weeks longer. And it will start earning at higher difficulty lower profits.
Yes, totally agree with your calculations.
I don't understand people who buy new S2.
They won't earn any money, except if they don't pay kWh (for example : plug S2 at work and not at home ...)
S2 is more expensive per Ghs than S1.
S1 can work during S2 delivery time...
S2 cost : 6.09 BTC / 1000 Ghs= 0.00609 BTC / Ghs
S1 cost : 0.988 BTC / 180 Ghs = 0.00548 BTC / Ghs, so a little bit more because S1 need PSU.
If Bitcoin value do not grow, people will lose money buying S2.
I'm wrong ?