You've mentioned in the past that, when constructing a WBS, 'Flatter is Better.' What do you do when you have a huge project that involves multiple phases like: Research, Pre-Clinical, Clinical Studies, etc.?
Pyramidic in Corning, NY.
There are two kinds of pyramids in the world. Most people automatically think of the Egyptian style and build their Work Breakdown Structures in this way. Their work is spread through out the levels of the WBS and it becomes difficult to keep track. Work is easily forgotten. Work that doesn't end up on the WBS is not considered part of the project. So, during the execution phase, when you get around to remembering it, you already have your project's cost and schedule carved in stone and you are in trouble.
If you've been to Central America, you may have seen squared-off pyramids. They have a flat top. Use this style for your WBS. Start by thinking of all your deliverables in any order that makes sense to you. Place them at level two of the pyramid, right below the project name. The activities go right below this second level. This allows for much more visibility and deliverables are less likely to be forgotten.
It's all about ensuring that, during the planning, you capture all the work needed to complete your project. Using this style, it is easier to ensure you have done so.
You bring up the point of very large projects where the list of deliverables may become unwieldy. For these projects I recommend using Workstreams: groupings of deliverables that make sense. For these projects, move the deliverables down to level three of the WBS and title level two with your phases: R&D, Preclinical, Verification, Clinical, Regulatory Filings, etc. Other large projects may find different titles for workstreams that group the deliverables in a more logical way. When done, your team can look at each workstream and verify that the correct deliverables are in each before determining the activities that make up each deliverable.