As I interpret the rules in regards to Wards and complexity, a PC could without too much effort (from a rules perspective) create a Ward with a complexity of 50 (or more!), given that he gets enough time. There are no limits in terms of the number of Declarations a Wizard can make (as long as he can explain them from a narrative perspective), so making 25 Declarations (to get 50 shifts!) should be OK (as long as his GM is agreeing to it). It would also be perfectly safe to cast the ritual once the Wizard gets a Discipline of 5+ (as at this level, he can feed 1 Shift of power to the ritual per exchange, without risk failing the spell).
The fact that a Wizard can succeed with any ritual as long as he is given enough time (and can explain all the Declarations) is fine by me in general, but when it comes to Wards it seems a bit strange (as the Ward is stronger the higher the complexity, and there are no real rules to prevent a player from (using the example above) that it is possible to create a way over-powered Ward.
It’s a bit off topic (but in a way related to super-strong Wards), but why would a Wizard, given enough time, ever use Fate Points or Consequences when casting rituals (when one, technically, can make an unlimited number of Declaration “for free”)?
I am thinking about putting a limit on the number of Declarations one can make when casting a ritual, but at the same time, it doesn’t feel good to do that. One the other hand, I would very much like the players to use Fate Points or Consequences when casting rituals, but when they have “free” Declarations, I can’t see any player ever using Fate Points or Consequences (given the Wizard have enough time to cast the ritual in question).