Great stuff, once again you feel the Buffy writers are making fun of the whole endless vamp love concept (Twilight/True Blood).
Please tell me you realize this was about a decade before that shit. Please.
Anyway, foreshadowing to be found in 3x01 "Heartthrob" :
In the flashback to ye olden days...
Holtz (to Angel): I don't have to kill you, you know. I could keep you alive for a long time.
Direct line to 3x22 "Tomorrow."