Lynks said:
Nagash's elixir still required you to keep on drinking it if you wanted to enjoy it's benefits though- that's how he kept his dreadlords in line as only he knew how to make it. There wasn't a craving for it like vampires suffer but still a need for upkeep. As far as I know, drinking the blood of a dragon stops your cravings but you still get to keep all the benefits.
Actually (according to the books) Nagash minions did suffer quite a bit if they did not get their Masters elixir every few months or so. The addiction it seemed to cause seemed to be even worse then what Vampires suffer.
Edit: The few months seemed to be the limit before they go bonkers, from what I remember "usually" they got to enjoy the elixir much, much more often then that. Specially during times of war when they needed the elixirs power to fuel them.
Quotes:
"The thirst was terrible. Every vein in his body was shrivelled and aching"
"The vizier tore the goblet from the mad slave’s hands and gulped greedily at its contents, all thoughts of war and conquest forgotten."
There is a throwaway quote by a von Carstein vampire in there where she comments on Dwarf blood being thick, flat and dull, and elven blood being thin and watery (and not very nutritious to boot). And thus neither being particularly palatable and desireable.
In "Neferata" consuming Druchii blood carelessly actually lead tooo:
"She was careful not to gulp down the blood that burst into her mouth, having seen the effects it had had on one of her handmaidens who hadn’t been so cautious. The vampire had collapsed as if drugged, and had yet to awaken."
Also Neferata being turned into a vampire was one wierd mix of...well everything. A flawed elixer, the poison of a phinx, Arkhams little ritual, the removal of her blood, the addition of Arkhams blood and then poof x)
Uhm also I might have missed the post but was there not a Vampire who got lucky and consumed the blood of an ancient dragon and his powers ( magical ) grew dramatically due to it?