Joel Spolsky wrote a great post on some of the hidden costs of software development. From Software Inventory:

The “cost” of code inventory is huge. It might add up to six or twelve months of work that is stuck in the assembly line and not yet in customers’ hands. This could be the difference between having a cutting-edge product (iPhone) or constantly playing catchup (Windows Phone). It’s nearly impossible to get people to buy Windows Phones, even if the iPhone is only six months better. A lot of markets have network effects, and being first has winner-take-all implications. So getting rid of inventory in the development process can make or break a product.

He goes on to propose an alternative to Backlog Grooming — one of the central tenets of Agile development:

The trouble is that 90% of the things in the feature backlog will never get implemented, ever. So every minute you spent writing down, designing, thinking about, or discussing features that are never going to get implemented is just time wasted. When I hear about product teams that regularly have “backlog grooming” sessions, in which they carefully waste a tiny amount of time and mental energy every day or every week thinking about every single feature which will never be implemented, I want to poke my eyes out.

His proposed solution is quite radical from an Agile perspective, and I’m not sure how it would work on large redesign/replatform projects, but it’s certainly worth considering.