Redesign is an inevitable part of maintaining a wiki. The impact of redesign can be lessened and the effectiveness increased by being aware that redesign will be happen at some point.
The best way to approach this is to build in a regular design review into the wiki maintenance check list (see Chapter 6, Maintaining the Garden). Also make sure to allow time in the project schedule for refining design work (you do have a wiki project schedule, don’t you?). That way, when a landscaping project becomes necessary it won’t come as a surprise, and time and resources will already be scheduled rather than having to be found at the last minute.