Back in Bonisagus' time, spontaneous magic was something that Diedne helped with. Interestingly, Rival Magic suggests Viea stole the notes dealing with the limit of Energy and fatigue, so Bonisagus never did get to work on integrating this sort of magic.
In terms of later additions, there was the idea at [url]https://forum.atlas-games.com/t/ars-magica-video-game/7312/21] that longevity rituals for mundane people are a late invention so you don't have huge numbers of mundanes with longevity rituals.