The great part about this one is that it doesnt have a cost limit on the instant, only that it be an instant and be currently in your graveyard
Pros : huge selection, flexible timing, perfect after a stabilizing turn
So, if some triggers go off between the resolution of Sundial of the Infinites ability and the beginning of the cleanup step, including those that trigger at the beginning of cleanup step, they all go onto the stack, the active player gets priority and then the usual chores
Lifegain also plays a major role in many white decks
Most people would just leave it at that
And if you want to grab your own inner or outer sleeves from Dragon Shield, you can use EDHREC's affiliate link to order some