The lifespan of each filter will vary based on several factors, including:
How Much Water You Are Using Daily
How Good The Water Is Where You Live
What Contaminants You Are FIlter Out (Certain filter medias have less capacity)
The Size Of The Filter
How Many Stages Are In Your System
In general terms, the average household will get about 12 months from a single benchtop system with standard 10" carbon block filter. Fluoride filters tend to have less capacity so need to be changed more often. The lifespan of sediment filters will really depend on how much sediment is in your water.