[ Astarion practically glows with happiness. Yes, that's exactly how he feels. An absence of Iorveth would be too terrible to bear. It seems very clear that the way his life has gone has been "no Iorveth = awful" and "yes Iorveth = pretty good"; an Iorveth is necessary for things to be all right. ]

Luckily for you, I've already cheated death.

[ Sure, that's discounting the fact that he very much can still die if (and when, probably) someone gets irritated enough with him to kill him, but at least that pesky old age won't get him. ]

Vampirism has its drawbacks, to be sure, but at least I'm not a hideous zombie like that Conway fellow.

[ He's referring to Connor, Mayrina's poor husband. ]