We are limited to putting out two Spirit Forges per chapter per year since it is a catalyst ritual (chapters may vary, but it takes a lot of attendance and finagling to put out more than two in a year). I see no game balance problem to someone using a Spirit Forge as the PC equivalent of a Renew if that is all they want to use it for because the supply of Spirit Forge is so limited (and in high demand). It would be one expensive Life spell ... over here in Seattle a Spirit Forge goes for a good chunk of change.
If players are using Spirit Forges mid-battle to get more Life spells then I would question the Plot that drove that player decision than the method itself.
Anyways, Marshals don't have the authority to answer the question if you need a rule to point to (because there isn't one written for a Marshal to reference). Additionally, since this isn't really a rule question and is instead more of a policy question, Marshals and ARC are not really the people to ask about this. If you truly need an authority to give a hard line in the sand then I recommend contacting the National Logistics Committee (Matt Watkins, username Auric, is the chair of the committee).
