Last night my team finished a project that took 5 years to complete (it may have been longer, but my brain is having a difficult time thinking in chunks of time bigger than 5 years, so let's assume it took 5 years). In the end there wasn't a lot pomp and there wasn't a lot of circumstance. The project moved step by step by step and dependencies were knocked down until the project was complete.
The odd thing about this is in many ways it feels like it just happened -- we just laid one last brick and realized all the bricks in place, and there is a complete structure here. Now I'm already onto thinking about other things -- probably the next thing that will take 5 years to complete, but when it is done will feel like it happened overnight.