Having held me in good stead all these years, the Boy Scout motto has motivated me to buy this, among other things over time. Better to have it & not need it than the converse. So, you can say today's episode is sponsored by the letter 'P' & the number '100'. Unopened, the filters are good for ~4 years. Once opened, the particulate filtration actually becomes more efficient over time, with accumulating filtrates adding to the effectiveness of the filters. For ~$40 - $50, it's a GREAT investment.
https://www.amazon.com/dp/B009POHLRC?psc=1&ref=ppx_yo2_dt_b_product_details
https://www.amazon.com/dp/B008MCUULW?psc=1&ref=ppx_yo2_dt_b_product_details