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Some of your subscribers may be receiving too many emails and ultimately may have disengaged from your communications. Limiting the number of sent emails to inactive recipients increases the likelihood that they'll open one of your emails. The logic is that your recipients are more inclined to open your emails since there are fewer of them in the recipients' their inbox.
A good practice is to create a triggered email ( Marketing+ > Triggered messages) notifying those subscribers that you'll be reducing mailing frequency. The Event trigger is setup with the condition to send the email if 90 days pass since their last click or open (as seen below). The copy of the triggered email can be something in the lines of "We've seen that lately you've shown little interest in our emails. For now, we're going to send you fewer emails and try to make or emails more relevant to you!"
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