one filter would easily last through a bad winter season. even if you stock 2 filters per unit, it would be fine. these are 10K rupee products (7.7K if you exclude the included filter). it's still totally worth it if you get 3-4 years of life out of them. i mean i am sure a lot of people are going to be pissed if mi gets out of purifier business and stop offering filters. i am going to be fine switching to another brand personally. this is not a novelty product that you buy for lulz. every day it runs, it provides good value.