From the Comprehensive Rules:
502.13. Cumulative Upkeep
502.13a Cumulative upkeep is a triggered ability that imposes an increasing cost on a permanent. “Cumulative upkeep [cost]” means “At the beginning of your upkeep, put an age counter on this permanent, then sacrifice this permanent unless you pay [cost] for each age counter on it.”
Cumulative upkeep has been worded like this for years now, and the Oracle text of cards like Cyclone and Heart of Bogardan have taken advantage of the usefulness of age counters to template their abilities.
- How'd you like Earthen Goo every time you pay the upkeep? What about Glacial Plating?
- How'd you like to Arctic Nishoba or Jotun Owl Keeper if you lose your fatty? (One of the most powerful examples of this was Vexing Sphinx, previewed over at Star City last week.)
- How'd you like to Hibernation's End or Phyrexian Etchings every turn you pay the upkeep?
- How'd you like to Herald of Leshrac?
- How'd you like a way to use cumulative upkeep to Jotun Grunt?
- How'd you like an Sheltering Ancient (three of the most joyous words in Magic) who eventually stacks up too many +1/+1 counters to stick around?
- How'd you like to Braid of Fire?
That's one way to make cost/benefit analysis easier—when costs are benefits.