Quick answer: Bug backlogs grow forever without cleanup sprints. A one-week-per-quarter sprint dedicated to closing stale or low-priority bugs keeps the backlog usable.
Backlog hygiene is rarely a sprint goal. Make it one once a quarter; the backlog stays manageable.
Pick a focus
Each quarter: a system (combat, UI, network) or a class (crashes, performance). Focused beats broad.
Triage day 1
First day: walk the backlog; close obsolete; reprioritize stale. Surface what's actually worth fixing.
Fix days 2-5
Engineers pick from the focus list; work in pairs for hard ones. Bake low-priority bugs that compound.
Retro and report
End of week: what closed, what stayed, what came up. Pattern in the patterns is the lesson.
“Backlog cleanup is maintenance. Maintenance is cheaper than the alternative.”
Schedule the next cleanup sprint at the end of the current one. It always happens; calendars don't drift.