Cancellation (aka Early Termination) is an enhancement for Affliction (advantage) found on page 13 of GURPS Psionic Powers in 2009.
in 2005 PK mentioned the idea: http://forums.sjgames.com/showthread.php?t=4645
- Variable (+5%) lets you hedge your bets before using an ability, letting you pull back your levels to reduce the duration before you attack. The ability to cut your Affliction's duration after rolling is more useful, since you can use full power and then dissolve it at your leisure. Thus, this should cost +10%, IMO.
After that in 2006 http://forums.sjgames.com/showthread.php?t=17145
- Variable allows you to "pull your punch", which can reduce the duration of the affliction (assuming multiple levels) by reducing the effect of the subject's resistance roll. I'd call the ability to reduce the duration as an afterthought about twice as powerful, or +10%. It's not Switchable, but its own unique enhancement, "Early Termination" or whatever you want to call it.
in 2007 Kromm approved post-activation Switchable (which is the same cost at +10%) for releasing people from Binding: http://forums.sjgames.com/showthread.php?t=26352