Vampiric Touch and Shadow Word: Pain both benefit from something we call 'Pandemic'. This means that you are able to refresh both DoTs when they are at 30% or less of their duration without getting penalized for this. What this essentially does is extend the window you have to refresh your DoTs. As an example, Shadow Word: Pain lasts for 16 seconds, so its Pandemic is 4.8 seconds. In other words, the best time to refresh Shadow Word: Pain is when it has 4.8 or less seconds left and if you do so at or below this threshold, it will add the remaining time to the original duration. If you were to refresh Shadow Word: Pain when it has 3 seconds left, that would leave the new duration at 19 seconds as an example. Devouring Plague is a very unique DoT, but does benefit from certain refresh mechanics. Devouring Plague rolls over damage when refreshed, meaning that whatever damage the DoT has left when you refresh the DoT gets carried over and added as a multiplier to the new DoT's ticks. As such refreshing has no 'cost' associated with it, even though we spent the insanity to cast the spell. This should not really change your rotation much, just do not feel like you have to wait for the current DoT to finish before recasting it. You still want to try and refresh around 1s remaining to get maximum DoT uptime for our Mastery: Shadow Weaving.