I presume that this is a new construction project that is currently in the process of design and will be built with a possible completion date of 5 years hence...or more. Theoretically you will register the building at the begining of the design process and then upload 'design' credits to the GBCI while the design is being finalized. Construction will then begin and upload of those construction credits will take place at the end of construction. Of course that's all 'hopeful'. I would suggest that if you are considering deviating from this that you contact GBCI/USGBC with your proposed timeline so that you can get clear WRITTEN confirmation from USGBC/GBCI as to the timeline that you wish to follow.