I’d try to groom a Product Backlog aligned to a product road-map and capability release plan. And I’d restrain the team from getting too granular in the non-immediate Backlog items. There are some important reasons to capture ideas and not delete, not least the importance of respecting everyone’s capacity to think up better experiences. Innovation needs openness and divergent thinking without the fear of ‘No’ or ‘impossible’. People need a sounding board and, besides, a Product Manager’s time is better spent logging future ideas than arguing against why it’s not a priority.
That said, the fluid nature of markets today with digital disruption means there is huge value and an innate strength of Scrum and Agile to change priorities bringing up features and icing features from Sprint to Sprint. Emergence of new platforms, capabilities and social trends means that its better to work with a well cataloged backlog with attributed dependencies. Great innovations are often when two seemingly unrelated ideas come together to explode into something new and different. Amazon with Internet+Shopping. Uber with GPS-enabled phone + need a ride. 3M with Re-stickable glue + the post-it note.
Managing a product backlog of 5 quarters is reasonable so where’s your backlog if you delete anything thats not in the Scrum Backlog? Only when items in the backlog are feasible and prioritized are they readied for being worked on and should then be pulled into the Scrum Backlog.
To borrow from Eisenhower, any feature is either urgent or important. A good product manager knows that anything that’s urgent is rarely ever important and anything that’s important is rarely ever urgent. Working on deploying the capability dependencies up front for the important stuff never seems urgent and is easy to knock off a short-term Scrum Backlog. Giving people the space to innovate the future is ideally caught in a Product Backlog, Wiki or some tool to track dependencies and changing feasibility and shared with the team to record links, examples, comparative examples, PoC’s and prototypes. This is where great features can come alive and be sustained. Don’t give up!