Let's say a store is running an event in which the prizes are boosters from the current set
Once the ability resolves, the bonus applied by that instance of the ability doesn't change even if the number of permanent cards in your graveyard changes
For instance: Creatures (30) 2 Verdurous Gearhulk 4 Winding Constrictor 2 Rishkar, Peema Renegade 4 Walking Ballista 4 Deadeye Tracker 4 Wildgrowth Walker 4 Merfolk Branchwalker 2 Ixalli's Diviner 4 Seekers' Squire Lands (24) Spells (8) Seekers Squire only adds to the glut, and it doesnt help that both of the Explore payoffs also cost two
For a taste of just how much you can mess around with evoke triggers, check out Jesse Barker Plotkin's piece on getting the most out of cards like the Maw, Grief, and Fury with Undying EvilUndying Evil and its ilk
I tried to pick stories I haven't told, but there are a few favorites that I couldn't find written down in any articles that I might have told elsewhere (and it's just hard not to repeat anything with the amount of material I produce)