Some stoves require just a little maintenance to keep them operating optimally. Liquid or multi-fuel stoves often feature a generator loop where liquid fuel is vaporised. This occasionally requires internal carbon deposits removing. It isn't a difficult task if carried out before it becomes a problem.
The Katadyn BeFree filter has been a favourite piece of gear for the past five years. Unsurprising as it is light, compact, easy to use and has been successful in preventing me from getting sick on trail
Three Points of the Compass 