I was reading through my Legends of Hermes book, and noticed in the chapter on Contessa, that it states until the 900s, Hermetic magi had to use individual forms for wards, not generalized Vim spells.
This got me thinking, canonically, what else do we know to be limitations of magic in the early days of the Order?
I recall in a thread buried in the mists of time suggesting that early longevity potions weren't that effective on account of all the founders not living (at least being active) much past about 100 years past the founding of the Order, but never saw anything concrete. Any other little tidbits that anyone else knows of?
That wasn't how I read what was in Legends of Hermes. I interpreted that as that Vim magic couldn't ward against creatures, not that it didn't exist. It would have only been used to manipulate magic directly, but magi hadn't yet figured out that it could be used to keep creatures with supernatural power away.
From what I would deduce, it wasn't that Longevity Rituals were ineffective or not discovered, it was more like most of the Founders died before their time. Flambeau was suffering from old age rather early despite taking Longevity Rituals, which (to me) implies he had the major flaw of Difficult Longevity Ritual; so even a powerful LR would be of limited use, and perhaps at this early stage there weren't the experts yet that there are in 1220. No other Founder was described as aging prematurely or dying from old age while still at a (relatively) young age, though many died early or disappeared, often through foul play.
The main limit I would have on LRs is that there weren't many Corpus experts of great power or many magi with a Focus (per the virtue) of Longevity Rituals yet. The advantage perhaps though was that there may have been a lot of vis, which can add to one's LR. One of the prevailing theories about the alleged grand power of the Founders was that they had far more vis in their time than the Order today; or there was the same amount of vis but far fewer Magi.