It's the time of year when I have to start weeding (a more delicate term than 'purge') inactive subscribers from my newsletter mailing list. I have to do this about twice a year now.
Campaign Monitor tracks the number of newsletters opens for each subscriber, so it's easy to determine the rate of open of each. If that rate is less than a certain percentage, the subscriber is dumped. As I use a pay-as-you-go option to send out my newsletters, each subscriber costs me...and if there's no reasonable open activity during a 12 months period, then it's to the dumping grounds we go.
It's more efficient for all concerned, saves me money and un-clutters the disinterested subscribers' mailboxes. Last year, I weeded out about 300 subscribers. The total amount of weeded subscribers over the past 3 years is now about 900. Nothing to sneeze at!