[RPG] How Much Blood and Vitae Does a Vampire Contain

I'm relying here on what I consider a common-sense tautology: A rule that says that your traits may not be higher than X prevents your character from having traits higher than X. Extending the premise far enough to suppose a Storyteller would let you buy a trait higher than X under the presumption that temporarily raised Trait Maxima would permit it is, I think, generous enough.

As you posit it:

1. A vampire of the Eighth Generation uses Blood of Potency, garnering enough successes to lower his Generation to Sixth.
2. Having raised his Trait Maxima to seven dots, that vampire spends (as an example) 30XP [or 36, depending how you reckon "current"] to raise his Auspex to 6.

Now, eventually, the effects of Blood of Potency wear off, lowering the vampire's trait maxima back down to five. It is self-evident that you cannot use dots that you cannot possess, and there is no rule allowing for those dots to somehow go "dormant" until you raise your attribute maxima to a point where you could make them legal again. Therefore, the result would seem to be that your traits are reduced to beneath the new maxima, and the experience points to purchase them lost. ("Sanctity of Merits" doesn't seem to apply here, as Disciplines aren't Merits.)

Alternately, a Storyteller may decide that such dots go dormant, like those of a ghoul who has not been fed with blood for some time (no longer than half a year, then they start to decay). However, given the ease with which Blood of Potency can be invoked, this is an unlikely and probably ineffective workaround.

There is a built in limit to how many ghouls a vampire can have - their blood. Ghouls require upkeep in the form of blood, at least once a month and any time the ghoul needs to heal (if the vampire cares about helping the ghoul heal). They also need blood to power their own disciplines, should they have any, or boost their stats.

The simple fact that a vampire has to hunt much more to support more than a single ghoul is a natural limit to the number of ghouls they can have.

Now for your Ventrue feeding off his own ghoul before feeding the ghoul its monthly dose - the books even advise using that against the players. Ghouls of the Camarilla are known to the court and are quite often tampered with by other kindred. Feed the ghoul blood from another kindred, and have the Ventrue in question get blood bound to the other kindred. That behavior will end quickly... or not, the player character would be blood bound, so they might continue.

Additionally, Ventrue's weakness is well known. Kindred of the city might very well try to determine the character's herd based on what they know of the ghoul, there by cutting the Ventrue's food supply off in the city.

In the situation you are describing, the Ventrue is telegraphing to everyone how to hurt him by taking a ghoul he can feed off of, let alone actually feeding off of them. Let the natural consequences of that decision play out.

There is an additional check you can invoke if the prince of the city is not counted amongst your players - your players do not have the right of creation. The traditions explicitly restrict the right to create kindred to the prince of the city, but the creation of others of the blood is usually interpreted to include ghouls. It is the prince's prerogative to simply have excess ghouls killed off, strip status from the offending kindred, or even go so far as issue a blood hunt for a rampant ghoul creator.

Your main solutions in this situation are political; the books imply that this is one of the intended checks and balances against mass ghouling. Of course, this goes out the window in a Sabbat game, where you are supposed to create ghoul and neonate armies as a matter of course.