The three-pack is the best value, and it's the most affordable. The filter is usually replaced every 6 months, or whenever the light turns on. They are much cheaper than buying them at whirlpool
When I replace a filter, I always mark the date with a Sharpie. This makes it easier for me to identify when I need a new filter.
It is easy to install. I thought I'll purchase purerdrop water filter again, if they fit all my requirement.