This is one of the virtues from the RoP books which I often feel is more powerful than a minor virtue should be. It has great potential for abuse, as theorically it can save a boat-load of vis per year.
Consider Personal Vis Source, also a Minor virtue, which in most sagas only provides "about one tenth as much as the player covenant expects to gather per year at the beginning of the saga". In this saga, it would be about 6 pawns.
Consider also Mercurian Magic, a Major virtue that has some important drawbacks, which reduces the vis cost of rituals only by half. It can even be combined with Imbued with the Spirit of (Form), so that a Mercurian / Imbued magus could cast something like The Walking Corpse (ReCo 35) every 5 days at no cost in raw vis. That's the equivalent (in the most extreme case) of 511 pawns of vis per year combined (219 pawns saved due to Mercurian Magic, 292 due to Imbued with the Spirit of (Form)).
It is up to the troupe to decide on this, but I think there should be some sort of limit on Imbued with the Spirit of (Form). What do you think?
If you all say "No problem", then I will accept it. I'm just bringing a potentiel for abuse to your collective attention.