In Ian Andersen's book "Burning The Tables in Vegas", the chapter on The Ultimate Gambit advises to always insure blackjacks for cover regardless of count. What I can't tell is, does he mean insuring against all aces regardless of what the player has or always insuring if the player has a blackjack for even money?
I think that he means insuring all hands against an ace. After all, what good is it if you have a hard 16 and correctly insure against a blackjack and you don't do it at low counts when you have hard 16? This seems like it would get expensive though, always insuring every time the dealer has an ace. But perhaps it is not.