I've been considering a gearing dilemma lately. The 4-piece Holy Tier 7 set bonus (-5% to the cost of Holy Light) is really, really good. Insanely good, in fact.
However, you can't just wear Tier 7 forever. At what point should you break the set? Should you break it when you get your first upgrade, or should you wait to upgrade a couple pieces simultaneously? Maybe I should upgrade at the first opportunity, but keep the T7 in my bags, and swap back if I am having mana issues.