Right now, with Novas and Sundials, I have upgraded some but not all. Keeping some Novas lessens the chance of a congested hand in the beginning. Elsewhere, someone mentioned that upgraded Sundials are not targeted by permanent destruction, and that seems to hold up.
By the way, why are upgraded Sundials worse overall, in terms of cost, than basic Sundials? The upgraded saves one Time quantum for the initial casting cost, but it takes two more Light quanta for two Hastens. For the 1500 upgrade, we shouldn't get a card that is worse in some important ways.