I mostly agree with whatTuidjy said. I'd summon an Air Queen by turn 20 (in competitive game, you can't normally get more than one, unless most air and half-air nations are unclaimed), so I won't even try to summon another one (unless I have reasons to think that the opponents are not particularly strong)
I don't really rush for Ice Devils. You could get one by turn 12 or 13, but that would mean just researching the blood. There're plenty of Ice Devils, so the number you can get more depends on your blood hunting than on research. I'd rather go to Con-4, forge SDR and bloodhunt with cheap mages. I'd get to summon ID around turn 15-16, but by then I can chain summon them until they run out (losing 55 blood slaves is not nearly as bad as losing 50 air gems). With Con-4 I can also immediately field those ID with a good equipment. In my opinion, sacrificing everything to get ID by turn 12 is impractical. You can't even safely field it until you get Con-4 (except maybe Gaap).
With C'tis I may summon few bane lords if I get into an early war, otherwise I'd wait for Tartarians too.
I can't really comment on the wishing, because everytime I got there I already had the game more or less wrapped up. And when I wasn't getting there that meant I've died trying ;> Generally, I think that in the end game SCs become obsolete as solo SC. Anything will be destroyed if left alone. So I'm rather looking for a good Tartarians capable of complementing my armies.
I don't mind to lose SCs as long as opposition suffers more. Exchanging SC is welcome if I can produce new ones quicker
For example, if opponent took my province with his SC I may custom equip my SC with some expendable items tailored to opponents SC to kill him. Obviously, the next turn it's the turn of my SC to get killed, but that will also expose opponents force, so as long as I find exchange satisfactory, that's fine. This mostly apply to the late game, when it's between the last 2 major nations/alliances. Sometimes it works out funny though. I drop my SC killing opponents SC, he drops his killing squad, but my SC retreats. Round 2. I drop my SC killing opponents SC, he drops his killing squad and bunch of Ghost raiders to cut out retreat, but I drop my anti-GH squad in one of the provinces where my SC retreats. Round 3. I drop my SC killing opponents SC, he makes an assasination attempt with a puny guy. My SC retreats. Damn!
But all those strategy sometimes doesn't work so well. Few months ago I've lost no SCs, not a single major battle, while killing couple of opponents Air Queens, few Ice Devils and winning few major battles, but I've lost the game. How come? Well, he was expending less resources to wage that war and maintain the balance and eventually he has overcome me...