Make issue prioritization a habit
The best way to avoid backlog issue overload—is to constantly think about how it meets the team's priorities. In other words—re-evaluate all issues from time to time.
It may sound like a lot of time. But as it becomes a weekly habit, like a workout, you'll need less than 1 hour a week to keep your backlog in great shape.
P.S. Each of our teammates spends about 20 mins per week on issues evaluation.
Step 1: Go to board settings
All notification settings are individual for every board. Open a board, go to the upper menu, find Settings, and click on the tab Board.

Step 2: Set scores expiration time
Nothing lasts forever. The company's priorities are no exception. Something considered as crucial a month ago, can lose its urgency now, and vice versa.
Ducalis has a great tool: Issue scores expiration.
It means how often your team should read and evaluate all issues in the selected board.

It sets the number of days in which the scores will be reset, and each team member will have to re-evaluate the issues. Find the right balance between the frequency of priorities changes in your team and the number of new issues coming every week.
The rule of thumb is 3-4 sprints. Start from there. You can change it anytime.
Step 3: Connect team's Slack channel
Click the Slack button and choose a channel with all the members of the current board.

Step 4: Set a reminder
When should your team get a reminder to evaluate new issues? We recommend doing this at the end of the sprint.
For our team with weekly sprints, we set it to Friday's noon, as it's a great time to set back all your work and think about new issues. Somebody will always have a question or a comment.

Step 5: Get words of appreciation
When it's time, your team will get a message about who's keeping their issues evaluated and who is not.

It's a friendly reminder shared with the whole team. That tiny message can train each teammate to keep their issues evaluated to get appreciation in a public channel.