The current project I’m on has just finished the planning phase for the next iteration. We do 1-month cycles, with around 4-5 days of planning up front. This release I asked to have this reduced to stop us losing time on the fuzzy front-end, so instead we had 3 days of design which I think has proven to be enough for most of us. One group of features that had fairly complex usability considerations and was technically challenging will probably take 1 more day, but the rest of us are ready to “get real”. On the topic of design/planning vs. actual implementation I think The Onion said it best:
“Many in the area believe that Messner will fail and resort to burrowing a hole in the muddy ground where he will spend the rest of the season”