In Transylvania by Night, it talks about Libussa - the ghoul of Shaagra - feeding the sleeping Ancient any Cainites she can manage (especially Tremere). If she feeds the elder and then feeds from her every month, this would be doable. If it is a willing torpor, then the sleeping Ancient would probably stay asleep. In game terms, Shaagra would have an optional waking roll when feed after having a low Blood Pool, but could still choose to remain in torpor. This isn't too big a stretch if you want to crib these guidelines for a player.