Vanishing without a number means “At the beginning of your upkeep, if this permanent has a time counter on it, remove a time counter from it” and “When the last time counter is removed from this permanent, sacrifice it.”
July 13, 2013 · Magic 2014
Each absorb ability can prevent only N damage from any one source at any one time. It will apply separately to damage from other sources, or to damage dealt by the same source at a different time.
September 30, 2011 · Innistrad
If either half of the exchange can't be completed, the ability has no effect.
June 17, 2011 · Commander 2011
If either half of the exchange can’t be completed, the ability has no effect.
February 1, 2010 · Worldwake
Multiple instances of delve on the same spell are redundant.