Triggered abilities like the one on As Luck Would Have It will trigger only once
The only downside is that you usually do not want too many noncreature, nonremoval cards in your deck, and thus there start to be diminishing returns past the second copy
Its also a 6-mana artifact that doesnt do anything when you have an empty board, but it helps you to rebuild
A five-loyalty planeswalker that ticks up to seven when it comes down on turn three or four is a big threat, particularly as it can protect itself with a relevant downtick
Probably the best mythic rare battle card yet, it allows you to buyback three freaking permanents from the graveyard at a very, very reasonable casting cost
This not only stops board wipes, but also protects your things from targeted spells and combat damage too